Generally, Martin Logan and other ESL speakers are rather low in efficiency, and generally have an impedance in the 4-5 Ohm nominal range. So usually, they will benefit from more powerful amplifiers than typically found in a receiver. However, there is no need to buy high priced 'audiophile' amps. Professional audio amplifiers of today often are of identical technical quality, but lack the exotic cosmetics, but in exchange you get very high performance for relatively low price. For home use, I generally recommend Yamaha pro amps, such as the P2500S, P3500S, P5000S and P7000S(choose the one you want based on required power). I recommend these specifically because, besides top notch build quality and performance, they do not have fan noise to deal with (most pro amps have audible fans) and the rack mount ears are removable for use in regular width consumer audio racks. There is only one consideration you must make when using most pro amps including the Yamaha: the amp expects much higher line level input voltage than most consumer pre-amp RCA outs will provide. This is easy to fix: use a voltage converter designed for this very issue such as the Samson S-Convert. You run standard stereo RCA cables to the S-Convert from your RCA pre-amp source outputs. You then run standard balanced XLR male to female cables from the S-Convert to the pro amp's XLR inputs. Even the lowest level P2500S, produces far more power than most receiver's can. It is rated at 275 x 2 into 8 Ohms, or 390 x 2 into 4 Ohms, using the standard consumer power rating of 1kHz. So, it is best to compare it to most reciever power ratings based on these numbers. Actual, continuous power, is 250 x 2 into 8 ohms, and 310 x 2 into 4 Oms, 20Hz-20,000Hz(full audio band), both channels driven simultaneously. But at the same time, a receiver rated at 100 watts (at 1khz), may only produce 70 watts 20Hz-20,000Hz. Additional, the pro amp is rated for 4 ohm use constantly(and can easily take less), where most receivers are not intended to drive loads under 6-8 Ohms, and often those that do allow 4 Ohms, have an alternate mode they require you to use, that lessens output power, to prevent overheating at the lower impedance.
Note: I have used a wide variety of home audiophile and professional audio amplifiers. In my no hold barred sound quality main system in a dedicated listening room, I currently use the professional Yamaha amplifier series I recommended above.
-Chris
