Multitrack Recording - Which Interface?

Hi Folks,

I'm at the very beginning of set up and I'm unable to get to grips with understanding how to plug in multiple instruments into an interface that, once connected to a Mac, will allow me to record on separate tracks.

I've searched many products but I can't seem to find one that allows what I want/need. I understand a USB will only offer two channels so that particular option is out (Line 6 TonePort UX8 I thought was the answer but it's only USB) and therefore came to the conclusion it has to be firewire, and if this is the case then i need to find a list of products I could choose from.

The interface I'd like to work with should have individual volume controls on the front and at least four XLR inputs (and perhaps portable, even though a rack-mount may only be the real choice).

Here are some products that don't suit (I think):
Apogee Ensemble doesn't offer volume controls on the front of the interface
Apogee Duets is only two tracks
Line 6 TonePort UX8 I thought was the answer but it's only USB (it looked perfect although I don't need their built-in tones either even though it's great for latency because I wish to control everything in Logic)

Does this suit me?:
Focusrite Saphire Pro seems to fit the bill... so am I on the right tracks choosing such a product or are there many more I am unaware of.

Is there a one page list of everyone's needs concerning this problem? A spreadsheet perhaps (or am I really asking too much?). A spreadsheet of products would be a brilliant idea...

Am I missing something very basic and making it too confusing for myself or is this a standard beginner's nightmare?

Many thanks for everyone's help in advance.