Michael Soldano said in an interview that he prefers something like a V-Type to a V30 with a SLO. Eminence, WGS and Mojotone make a similar model. G12M-25 "Greenbacks" sound great, but roll off the high end a bit more, and may have less bass depth. They work with almost anything, but something tighter like G12-65's might be nice.
I know it's only part of the equation, but 5881 (beam tetrodes) are inherently more "clear" than EL34 (pentode) due to aligned grids and less 3rd harmonic clutter. AFAIK, the Mesa Dual Rec is a direct copy of the SLO100 with no neg feedback and cheaper parts. That or a 50W or 100W Jet City could be upgraded with a better OT (Classictone JTM45 or JTM45/100 0r 100W Project model?) to sound closer to an SLO100, but you need tight speakers to really hear/feel the bass punch a better OT will offer.
Signal path caps could be replaced for the type of sound you prefer. Mallory 150 metal film are apparently excellent (full and warm) and cheap. Some also prefer the more linear high end of a good silver mica cap for the Treble knob, if it doesn't have one. Those are all pretty easy and cheap mods that, along with choice tubes, should make a noticeable improvement in fullness, punch, high end linearity and clarity.
MS also said he always went through a bunch of 12AX7's to find quiet ones for the first few slots in an SLO100. The JJ ECC83MG is a very low noise tube with a smoother & more open sound than the standard 83S -- possibly the best new 12AX7. The ECC803S is a really nice PI slot tube. The combo of those types delivers a full, clear, sweet and dynamic sound for not much money. Power tubes are your call. JJ or Tung Sol 5881 are probably the best of new 5881 tubes -- the JJ being "harder" with less high harmonic generation. I've heard great things about the new Tung Sol 7581A -- like a cleaner & fuller sounding 5881, but not boomy like a 6L6GC. A bias adjustment might be required. I've read the JC heads are biased very cold from the factory anyway. You might also try a resistor-based 10% power or PPIMV mod as well. Those are easy/cheap mods as well. Anyway, that's what I'd try.