CoryGillmore
Headphoneus Supremus
It doesn’t have to cost an arm and a leg to feed them quality power. But yes, upgrading from your AV receiver is kind of a must to do justice to these great speakers.
I actually ended up with an audiolab 6000a Play and it's totally badass for a roughly $1000 amp. Oh I also rearranged my room to put my speakers on the long wall and get them 11 feet apart, center to center. Fantastic decision.
I used these Cornwall IVs for about 7 months with no subs and enjoyed the hell out of them. But then I hooked up my cheap home theater subs and got them dialed in. Crossed over at 40hz and still running speakers full-range, as one should IMO. The subs pickup just where the Cornwalls fall off in my room, on some tracks they don't even do anything, and on the tracks that do get them going they don't draw any attention to themselves. Fantastic integration.
At the moment I'm planning on getting a pair of REL T9/x this summer. I'll run them from their high-level inputs, right off the Cornwall speaker taps. One sub for each Cornwall. It will be glorious. I barely listen to headphones anymore unless I'm at work.