I really haven't experimented with my iMac too much because it's my son's machine, but I think you should be able to run 5 for pve easily. I'm not sure if its gonna be beafy enough for pvp. But my limping G5 runs 3 well and 4 well enough to play. I have managed to "hide" the windows using the menu on the dock but I can't seem to minimize the wows. Personally, I like putting my windows back a little so I can see if they quit following, but it'll hurt your fps a little to have all that video going on. Of course, you don't care what the followers' fps is. I had all mine on 800x600 but mostly so they would fit on my screen. Everything turned down except for sight distance and I have to have sound.

P.S. I'm still planning on updating the summary again soon. Adding some new software options and relating on my new 4 box setup. I think a how-to for synergy would be nice if you have a cross-platform setup like mine.