I had bi-amped for years using Rotel RB971 power amps, with a Rotel RC971 Pre amp. Around a year ago I upgraded the power amp to a Audiolab 8000Q which made a huge difference. I had pondered for a long time about bridging the power amps and converting them into monoblocs, I finally bit the bullet earlier this year. It was the best upgrade I made and it was free, only having to move the appropriate jumpers on the power amps. This may be worth you considering if you are determined to add another power amp to your set up.