I'm using my FX8 with a Hughes & Kettner Grandmeister 36 with powersoak down to 18, 5 & 1 watts. Am currently running it at 18w but am going to try 5w so I can push the master a bit more - we mic cabs for gigs anyway so it doesn't need to be crazy loud.
It's a lunchbox amp and I've just switched from a 2x12 cab to a 1x12 - which sounds even better, so my rig couldn't get much smaller now unless I switched to an Axe FX into the PA.
It's worked with the FX8 with zero issues from day one. It's got full MIDI Control with 128 presets and everything saveable per channel, EQ, Prescence, Resonance, Gain, Volume, Reverb, the whole lot. It also has built in effects which are also saveable per preset. They're actually pretty good, but unsurprisingly since getting my FX8 I haven't used any of them other than a little reverb on a couple of presets where I had run out of CPU. Since firmware 3 though - and probably getting to know the FX8 better I'm not using any of the amp's effects at all now.
I'm extremely happy with my sound and have only really had time to scratch the surface with the FX8. Even so I've had numerous compliments on my tone since I started using the FX8, so it's clearly very compatible with - and enhances my amp.
I've now sold most of my old board which included a Suhr Shiba, Koko Boost, Wampler Ego, H9 & Strymon Timeline. I can't say I miss any of them. My guitar sounds better and is super quiet too.
I hope that helps. Definitely worth checking out and used prices are low. Good luck.