Amp for Acoustic Zen Crescendo 2 ?

Wlutke,
Audiogon member named "Wig" has these speakers and has driven them with Vac mono blocks and then the solid state Vitus amplifier. He currently uses the Line Magnetic 508ia and finds them the most satisfying thus far. I’d get in touch with him via audiogon email. He’s quite experienced and knowledgeable. As Grannyring astutely wrote musical genre, room size and listening volume all are factors to consider in amplifier selection. I’ve heard these speakers at shows on 4 separate occasions driven by the Triode Corp TRX 845 PSET mono blocks in spacious rooms and they were glorious! Builder Robert Lee has used them for obvious reasons, primarily because they mate brilliantly together.
Best of luck,
Charles

Thanks everyone for the responses.  I listen to pop/rock/other in an 15x20x8 room at moderate levels.  Just loud enough to energize the room, not rock the neighbors.  It's a condo.  The Line Magnetic 508ia looks interesting.  Monoblocks are generally too large for my rack and no room on the floor.

Wlutke,
The LM 508ia uses the 300b as the driver tube and 805 as the power output tube, 48 watts pure class A with SET topology. I hope you are able to contact Wig as he can share "actual " owner’s impressions of this amplifier with your Crescendos. He's ecstatic with the sound quality. 
Charles

Thanks for getting back. Well then yes the Line Magnetic and LTA ZOTL 40 should work great for you. Two great choices. If you dont want to mess with tubes and all that goes with owning a tube amp, then Pass Labs makes some great amps that you could afford used. The 250x for example. The Lyngdorf 2200 is amazing also and runs cool while being light and small. Only $2400 new.

Electrocompaniet makes some of the very best sounding SS amps on the planet. Harder to find used. The McIntosh 402 amp is also very special. Finally the Conrad Johnson ET250s is great sounding and will deliver exactly what you are looking for based on your post. It is a hybrid amp that uses small signal tubes on the input section. Sweet sounding, yet is has the power to control and open up the AZ speakers. The signal tubes are not expensive and last for for many years. No problem running the amp for long periods of time. $2999 new from Spearit Sound on sale. Great price.

I have had better luck with more SS watts on the Crescendo as the speaker just sounds more relaxed, in control, and bass powerful with plentiful SS or hybrid watts. Great quality watts as my suggestions are.

The VAC Phi 200 would be worth a strong look given the attributes you're looking for, and it's available used in your price range.  Also, call Acoustic Zen and see what they'd recommend.  Best of luck.