Quicktime Input is always mono?

Does anyone know what´s the deal?

If I understand you correctly, it sounds as if you work flow defaults to a "mono" channelization setting. It is still unclear if you are getting two "mono" channels or just one. QT 7 "Pro" (if you have it) would allow you to re-designate a "mono" channel as a "right" or "left" channel. If you have two "mono" channels, then one could be designated as a "right" channel and the other as "left." This does not, however, ensure the content is "right" or "left" if your work flow/hardware actually mixes the 2 channels before digitizing/recording the audio.

As to true "panning" control, the QT 7 Player has a playback "Balance" AV control which QT X lacks but only a sound editing application like GarageBand has actual input "Panning" controls for each channel for output targeted re-mixing.

Does anyone know what´s the deal?I know about the balance control of QT pro, but that´s only for playing clips and does not affect recording.

The QT 7 Player "Balance" control is not the same as the QT 7 "Pro" channel use control. You still have not indicated if you are dealing with a single channel in the target file or two channels. You still have not confirmed if the output file is channeled for "mono" (center channel) playback or not. In addition, there is the question of whether or not the results of your unplugging one channel of your Audiofire input and manipulating the pan control is in any way significant since the panning of one channel and then designating it as a "mono" channel would result in the same change in volume whereas if two stereo channels were both re-designated as "mono" channels, then as the panning is applied, the one channels volume would increase as the other attenuates and would then provide a more or less constant volume when the two "mono" channels are played back together.

Since you seem to be unfamiliar the channelization attributes of QT 7 "Pro," I would suggest you post a sample snippet of a test clip recorded with both Audioifire input channels active and applying a "panning" action. Then someone here can look at the file in the "properties" window and, if necessary, re-designate the output channels as stereo Left/right to see if the the pan is audible in the final output or simply confirm that the channels are being physically mixed. In the latter case, I would tend to believe the problem is either in your hardware device or an encoding/capture setting since QT captures normally default to a Stereo Left/Right channelization if two inputs are present and you have not manually set the QT capturing/encoding app to a single "mono" channel setting.

There´s nothing I could find up to now about quicktime and stereo recording.

A QT MOV file container can handle up to 99 data tracks. Theoretically, this could be one video track and up to 98 audio tracks any of which can be designated for any of the following uses:
a) Mono
b) Left
c) Right
d) Center
e) LFE Screen
f) Left Surround
g) Right Surround
h) Left Center
i) Right Center
j) Center Surround
k) Rear Surround Left
l) Rear Surround Right
m) Left Total
n) Right Total
o) Discrete-0
p) Discrete-1
q) Unused
Since audio can be layered, multiple independent tracks can be "logically" mixed by designating the same speaker array use. Your ability to use these channels is, of course dependent on the amplifier, number of speakers, and how they are arrayed/wired for playback.

Can anyone say clearly that quicktime can make a video recording (firewire dv cam plus other mics) in stereo? Even the camera mic that´s a stereo one (that´s a sony DCR-TRV125E) is recorded only in mono mode.

My board supports up to 6 independent audio channels simultaneously and I have seen others that handle up to 8 channels. As previously indicated, what you can handle depends on the hardware, software, and available settings used in your work flow and you should be checking the user manuals/guides for these items as any recent platform should natively support stereo inputs as a minimum without the additional support for third-party hardware/software.

May be I´m chasing a ghost?

No, but your unwillingness or inability to answer direct questions or provide a sample file for analysis makes it difficult to determine whether your main problem is one of "physical" or "logical" down mixing of content. As a result, I fear nobody here will be able to help you.

Here I´m trying to find our where´s the mistake. Is it me, doing something wrong, or is the driver of audiofire 2 not right, or anything else?.

It is possible that you are doing nothing wrong and your results are simply the way your work flow works. For instance, your hardware may only physically export mono audio. On the other hand, it may be exporting two separate audio channels that are, for some reason, "logically" designated as "mono" content which plays through stereo speakers as mono content. In the former case you would need to change your work flow. In the latter, you may only need to change the "property" setting in the captured file to play the content correctly.

Even the camera mic that´s a stereo one (that´s a sony DCR-TRV125E) is recorded only in mono mode.

The DCR-TRV125E user manual indicates this product records in the same stereo format as my DCR-TRV520 and HDR-HC3, both of which recored in stereo to my system when connected directly to the platform. So, if you camcorder records in stereo when connected directly to the system but in a single mono channel when connect to your Echo Audiofire 2 hardware, the logical conclusion is that the Audiofire is causing the problem. (If the camcorder records in as a single "mono" channel when connected directly to your system, then QT X and/or your OS would appear to be corrupted.) However, this still doesn't tell me if this device is physically mixing the audio content down to a single channel or if its output is seen as two independent "mono" channels (which can be "fixed") when captured by QT X but as Stereo L/R channels when captured by alternative capture utilities.

As repeatedly indicated previously, your first step is to explicitly define the nature of the problem before you can make an attempt to solve it. In tests run on my Snow Leopard system, it was impossible to record a mono audio track even when I plugged in and selected both a mono mic (audio) and the DCR-TVR520 (video). The audio still came out as a "Stereo (L/R)" even though both channels contained the same audio data. Therefore, let me ask one last time how the QT X inspector (or if you have it, the QT 7 Pro "Properties") widow is describing the audio track for your "mono" audio. If you cannot answer this question, simply post a sample file for analysis.