I'm wrestling with a similar situation and have yet to nail it all down.
My equipment: HD5870
Silverstone Cw-03 (7inch vga lcd) connected thru dvi/vga adapter. Elite 101fd plasma connected thru hdmi . HP L2335 connected thru active display adapter/displayport. Pioneer sc-37 AVR
the main viewing area contains all the equipment except for the hp screen which is on the other side of wall of all the equip (different room). Cable lengths are short. Also have a wired mouse/keyboard running thru wall. Ideally I want to game/work in small room and htpc,light gaming in main viewing room using my 1 pc.
I am having issues tho. I never use all 3 at the same time. I love my case but in hindsight wasn't the smartest move I've made. All it is, is eye candy. Doesn't get used at all. It also makes multi-monitor setup a pain. Windows keeps juggling my monitors, hdcp issues and now unless i disable the hp monitor, live tv doesn't work in 7mc. And this just started happening yesterday, if I turn off the plasma, my hp goes to sleep......wtf.....
Anyway I'd be interested on how this all works out.
You guys think an hdmi splitter will work out better than using the displayport for HP monitor (since these 2 screens,plasma and HP, will always be duplicated)