I used the Eventide Pitchfactor, Peavey Cel 2 Compressor, Palmer PDI-09 (with an adapter to convert XLR to TRS), Sansamp PSA-1, Peavey Rockmaster, Mesa Boogie Quad. The nice thing about Eleven Rack is you can slide that FX Loop anywhere you want, so it's very versatile although overdrives and preamps are just better to use into the guitar input unless you want to split the outs so there's a different thing on the left and right. I used to do a thing with a delay pedal that had a dry out and a wet out for subtle widening effects (only using a compressor or PDI-09 on the left or something). All in all, I learned to just like the Eleven Rack for it's own amps and effects, BUT I did like to use a Behringer TO800 going in, even when the pedal was off, it boosted the signal a bit. A clean boost or pedal is going to change the sounds more than anything, even the effects are different sounding with a tube preamp or green overdrive. They are indeed, top notch. The Eventide stomps have an analog filter and work great at the EVH widening effect and doubling and things of course, but the quality will only match your guitar sound so that should be your #1 priority is get that dry tone first. And if you can tweak the left and right to sound different, the effects are "bigger." Even an EQ in the effects loop would probably make a big difference.

The #1 thing I would get if I had the choice is that Logidy Espi C and put that in the loop for cabinet sims, then the on board effects are gonna change dramatically.