I have the Signature Platinum modded 3910, and had a Platinum modded 999ES prior to that. I am sending the 3910 in soon to have the ps tube rectified.
The Modwright highly modded 3910 is an incredible machine that bests the stock player by 80%, that is to say it sounds nothing like it. It is detailed and resolving, yet has a smoothness that has to be heard. It is that smooth analog quality (sorry, trite I know, but can't think of anything else to describe it, and the OP is desperate for opinions) that had me hooked on the 999ES and then the 3910 takes it 10-20% farther. I haven't heard the tube-rec'd ps, but can't wait to live with it. Also, one can go the Wayne Donnelly route and plug in expensive Bendix 6900 tubes and live the high life.
I use the 3910 for all my spinning disc needs , especially SACD and DVD-Audio, both 2 channel (tube modded) and mch (slightly modded with newer op amps). It is also my redbook benchmark and is what I'm trying to replicate with a Slim Devices solution. Right now I'm only 50% of the way there with a RWA-modded SB3, a Monarchy DIP Upsampler, into an Ack Dack. The remaining 50% + (can always dream) will be likely solved via Dan's Transporter mods!! The 3910 has set a very high bar for redbook, but I'm so use to the convenience of the SB3 that I only use it for those special times when those special cd's I must hear in all their glory.
I would highly recommend any of Dan's work.