OK, what if your friend's answer is: "I want to do some photoshop work, play the occasional Windows game, and also hook up a PS3 for games and blu ray movies."
You want to hook up a PS3 to a computer? Why? If you want to use the screen then you would be better off getting a cheap 32" LCD. I think they would be happier separating the PS3 from it.
Trust me, I can certainly be accused of trying to make a computer do far more than it should. I think one has to keep your goals in perspective.
I bet Dell could configure a PC more powerful than the Mini which would be fine for games and cost a fraction of what the Mac Pro costs. Plus he could get a monitor which supports HDCP and multiple devices.
...and what OS is it going to operate on? Kinda kills the whole point.
I would have no problem recommending an iMac to most anyone for home use. If they are a hard-core gamer then they need to just build a PC. A MacPro is not even that great of a gaming system because it's not tweakable. Otherwise, there is a solution for pretty much anyone.
-mx