I've had a pair of Acoustat 2+2s since the mid 80's. I went the full gamut of audiophile products: Mosfet, bipolar, tubes-push/pull and DHT single ended 45,2A3, 300B). The single ended Loftin/White 45 was the best amp driving 96db Infinity Composition Preludes (first model). The Acoustats like power but be careful with the low frequency transformers arching over on the secondary (see posts on TAC-The Audio Circuit). Exotic tube amps and preamps with premium NOS tubes were to my ears the best. With the Acoustats you need a very high quality front-end to get the best out of them. Remove socks, put the BEST coupling caps you can afford in the high pass crossover, use Caddock heatsinked Power Film resistors to replace the high pass variable resistor, connect the series fuse only on the low frequency transformer and go to a fast blow instead of slow blow fuse (those silver fuses may be worth a try), use spikes if you have room to couple the speakers to the floor, AND place the speakers out from the rear wall at least 3' or more! These speakers are extremely finicky with placement (sweet spot is VERY tight). I have the spectra 44 interfaces and hope to one day convert the 2+2s to the 4400 (should improve high frequency dispersion). Also look for the improved panels per Andy (Acoustat tech), they will have a yellow/red strip for the bias wire. Currently I use a highly modified all tube counterpoint preamp, extremely modified tube output stage CD player, and a modified 6DJ8,6SN7 Moscode 600 type amp (also have two enormous custom tube/mosfets amps with Krell heatsink in the works). Great speakers. After trying mid level sensitivity 87-89db speakers with tube push/pull amps and the high sensitivity >95db speakers with DHT S.E. amps, I decided to go back to the Acoustats. Now if only I could get a DHT SE 45 amp to drive them....oh well, you can't have everything.