@tykozen - You have A LOT of terrific recommendations. Reading through them, if you decide to go with separates I agree with the posters who say ATC sounds better with a solid state amp. In which case, getting an Ayre or Pass and pairing them with a tube pre-amp makes a lot of sense because Ayre, and Pass have both the power and tube-like qualities you desire.
As far as pre-amps go decide on your overall sound preferences. Kinda like martinis-very dry, with a hint of vermouth or full flavor. You could go highly resolving and neutral--in which case get solid state amp and pre-amp; resolving with the soundstage a tube/JFET pre-amp will provide, or full tube pre-amp, which have more bloom/euphonics/"more musical".
I'll end with YMMV, because everyone has their preferences, and there are so many good amp/preamp choices and combos.
David

