Fishcall, despite what others say, I think you're on the right track. I don't know about your 3802, but in my 5800 the power amp is the bright-sounding part. The preamp and DAC are pretty neutral. By adding a warm sounding power amp to your preamp outs you may achieve exactly what you want. Try some Audience AU24 ICs to connect them. This IC is superbly neutral throughout the bass and mids and rolls of the treble a little. Cardas cables also work well in this situation.
Whatever you do, don't buy Bryston. You'll be worse off than you are now.
Whatever you do, don't buy Bryston. You'll be worse off than you are now.