I use the compressor in the FX Loop on the Mesa Subway Plus DI (after EQ).
I found that before the EQ, there where too many things I didn’t want to ear on my final sound (fret noise, string buzz and so on). When I placed the compressor after the EQ, my sound was much more natural and as I always wanted. I also noticed that I compress a lot less after EQ.
For me, after the EQ is the way to go but it might be better if you try both ways and figure what’s good for you.