My friend bought a used Marantz 2220B (circa 1975) receiver (http://www.classic-audio.com/marantz/2220b.html) from a flea market. It is rated at only 20 watts a channel. Will it be enough to drive the M40s he already owns, or will he run the risk of clipping? It's my understanding that Marantz was known for manufacturing a robust receiver. I hope it works, 'cuz all sales are final, and he already owns the M40s, just no receiver or amp until now. Thanks!