I agree with the consensus here that there really isn't a pedal or tube pre that will exactly replicate what an all-tube rig does at high volume. The tube rig isn't just about tone, it involves feel issues, volume issues, compression issues, etc.... It's also unfair to expect a pedal to replicate such a tone when your listening through your home practice amp or computer speakers! Or, I'd go so far, playing through a 350w ss amp and a 2x10 or 1x12.... It's just not the same (to me, YMMV). All of that said, however, I did buy an EBS Valve Drive for one major reason. Sometimes, when I fly to a gig, I don't get my requested backline rig. Often this means a super-clean ss amp that doesn't really sound how I want (not that I can't make any amp sound good - that's another discussion). In these instances, the Valve Drive makes a huge difference for me! While I'd never claim that my Valve Drive makes a GK head sound or feel like an SVT, it goes a long way towards accomplishing that goal. There are certainly other options as well - I have an old Mesa V-Twin that sounds incredible through ss gear as well! Another (non-pedal format) option I've always wanted to try is the SWR Interstellar Overdrive rack pre. It has an actual low-wattage tube power section connected to a dummy load that is intended to give you true poweramp-type distortion. Warwick also has a bass head that incorporates this concept (I'm sure there are others).