Thanks for the info. I found a used STP-SE offered for $1200 and snatched it up. I should get it early next week. I may have jumped a bit too early though, as someone put up a CAT SL1 Signature Mk2 at 2700 asking and I wonder if that might have been a better choice. After a boatload of system setup work, my D-Sonic amps are as much fun as the expensive tube amps they replaced. I am considering letting the STP-SE settle in for a few weeks then send it in for a Level 1 upgrade first before selling my old Classe DR6 preamp. I suppose I'll never know if the old Cat would have been better.