the cheapest amp to drive watt/puppy 7

I have owned the BAT VK-300se, McIntosh MA6900 and Krell KAV-400xi, all at approx. the same time. All three were used to drive a pair of Wilson Audio Sophias, and all worked very well at moderate listening levels. The BAT may have sounded the best (tonality, clarity, texture & holographic-sonics) up to low>moderate volume-levels, it went into shut-down mode twice, and went through 2 tubes and 1 fuse, in the brief time that I owned it. The McIntosh sounded nice in a classic hi-fi sort of way, it didn't strive to be realistic-sounding as the other two amps., it was too laid-back and uninvolving for me. This amp. simply did not provide the imaging, dynamics and bass that the Sophias are so capable of, and would shut-down (protection) when driven to moderately high levels. It did however have very good microdynamics and was always pleasent sounding and never harsh. The Krell worked best in my large listening-room and with my listening preferences. It had very good imaging, dynamics and bass, it filled my 5.5K+ cu. ft. Room with sound, and it never ran out of steam, blew-a-fuse or shut-down, with the right source material, it was quite realistic sounding. I believe that the Krell retailed for less than half the cost of the other two Amplifiers. This is where I would start.

I can attest to the fact that the Audio Note Meishu amplifier is among the best I ever heard but at (an extremely robust) 9 watts you would not rock out with the WPs.

Every post I ever read on the subject seems to agree they are not especially efficient despite their friendly specs.

I've driven my WP7s with a Music Reference RM200 for five years and it is an excellent match. The 100 or so watts that it produces is enough to rock out with in my modest listening space, but it is equally good with opera, orchestral, jazz and blues music.