One of the best, if not THE best, integrated amps on the market today is the Musical Fidelity Tri-Vista 300, which is reviewed in the most recent issue of TAS. The Tri-Vista 300 has a superb preamp section, and the power amp is rated at 350 wpc. Unfortunately, it sells for $6000. If you have the time and patience to try to find a used model or a demo, it's worth considering.
