To me Bi-amping is hard with two different amps, you have to keep in mind the different gains, and the input sensitivity of the different amps, to try to match the levels so it sounds right. Not to mention the different input impedences, and the output impedence of the tube preamp interacting with each input stage of the amps! Plus you are loading down a tube preamp with TWO amp inputs, as well, argh.
Its too complicated for me. I personally would sell the MF and buy monoblocks, or a big amp if you need more power. The idea of monos appeals to me as they are identical, you give each stereo channel a separate power source, and signal path, so there is no chance for cross-pollution, and maybe a better stereo image. Also I like shorter speaker cables. Also, you might experiment with an upgraded source. Maybe that is your weak link causing the brightness. try a few high end CD players in your system first. If your source cannot produce smooth sound and good bass, more power will just amplify a bright sound. I myself have always wanted to try tubes for the tweeters and mids, of my Revel speakers, and solid state for the woofers, but these variables drove me crazy.
