ARAGON 8008 MK.2 or McCormack DNA 225

Exertfluffer,I have to disagree about your comments about the Adcom GFP-750.It is the most transparent preamp I have heard any where near its brand new price [approx.$1500.00].
It is extremely open,detailed, and transparent.Maybe a little clinical,but really great for the price!
I took mine to a friends house who is using Revel Ultima Studios, Kimber Kable Bifocal speaker cables, Kimber Silver Streak interconnects,Sony SCD-XA777ES SACD/CD player,Music Hall MMF-9 turntable, Musical Surroundings Phenomena phono preamp, Krell KAV-250a power amp, and a Krell KAV-250p preamp.We were stunned by how good the Adcom GFP-750 sounded in his system! It was more open, transparent, detailed and focused than the Krell preamp! He also tried a friends Audio Research SP16L preamp, and the Adcom bested it by a good margin.It may not have deserved a Class A rating, but its a shockingly good preamp for the money.I became a true believer in it yesterday!It sounds better by a wide margin than the many preamps I have borrowed and tried in my system also.

As far as active solid state preamps go, is the Pass Labs x-2.5 preamp alot better sonically than the Adcom GFP-750 preamp?

Actually, I've sold both in the past. I think the Aragon isn't that extended actually. The McCormack is slighly better IMO for most applications. and is more neutral sounding for your otherwise "warmish sounding" Studio 100's!
Also, don't waste your time with the Adcome 750(suggestion). It's hightly over rated and mis-classed!(more like "Class C" in my experience from selling it/using it!!!
There are many better chioces for the same money. If you're going to do "passive/pure" preamp chioces, finding an old Pass Aleph L/P is much better! It's got no dynamic "pick-up" like any passive, so you'll have to judge your mix. Otherwise, there are a lot of very good potential tube pre's out there that might give you the sound you need. good luck