My experience is limited to the SP-100, but I have found it to be very flexible concerning amplifiers. I have used it with amps ranging from 300W per channel (Classe CA-300) to 1.5W (homemade single-ended 46 amp). In between, I've used a number of push-pull EL-34 and KT-88 amps, as well as 300B single-ended. The Spendors sound very nice with all of the combinations. Overall, I prefer good tube amps on the SP-100, but the power doesn't seem too critical. I'll admit it needs more than 1.5 watts and a single 300B is sometimes not enough, but anything in the 15 to 50 watt range can do fine. The quality of the amp is more important than the rated power.
