Convolving for guitar cabs?

hi guys

so like many i've been messing with plugins such as amplitube and guitar rig. well personally, they all sound like crap...and many have discovered if you put an impulse of a real guitar cabinet after the plugin, it turns it into a completely beleivable guitar sound

However the PROBLEM is on mac, there arent a whole lot of convolving plugins. im using one, called LAConvolver...problem is i think it's a weak link in my chain, as a all my guitar sounds are terribly thin!

Im recording from a rackmount preamp (boss GL-100) usiing a nice thick fat clean tone...recording from the monitor out into my Firewire audiophile..which is more of a DJ/Phono interface, but it works

There was a nother convolving plugin for free, but god is it buggy...cant even get sampling right

ive tried using space designer with impulses from guitar cabs, however it always seems to add a bit extra or be a bit..well, still reverby....how can i make it so that it does nothing but convolve the signal and nothing more? its always seemed to add alittle more noise or hiss than the other plugin...

i havent updated to logic 8.0.2 yet..been forever since i've played with it to tell ya the truith