RLL -
If you like tubes I don't think you can go too far wrong with that combo. I have the std Song Towers, orginally driven with an Omega 250 & T-8, and it's a fine pre. That system now driven by a FetValve 550 & Ultra pre combo, which was definetly a step up. Haven't the funds to upgrade to the 600R at this time, though a friend just sent his 550 in for it. There may be a person or two that has that specfic pairing, but I don't think you'll find anyone who's been disappointed with the T-8 (now runs my office system). And any upgrade from the 550 is bound to be sweet. At the very least it's worth checking out to see if it meets your tastess, you can always return.
Happy Listening - JD