Usually I would build my own system, but I have moved 500KMs out of Sydney and thus getting parts is an expensive ordeal, so I've had many a discussion with the owner of OzCustomComp, which is an eBay store, and buying a pc over eBay doesn't sound as dodgy as I first imagined.
Are you sure building it yourself wouldn't be cheaper? The rig's going to be about 15-20% overpriced.
If you do decide to get this, you don't need to upgrade the PSU unless you don't trust the standard CM model for some reason. The mobo isn't any good for CF, and there's no reason a 650W PSU would be insufficient for a single 5850, if that's what you're thinking.
Be aware that when you buy a card like the 5850 preinstalled in a system that is shipped some distance there is a great likelihood that the card will become unmounted and damage your motherboard in shipping. I have seen them snap the pcie slot clean off.
It will be travelling 600KM's. I am aware that some damage is possible in transit, but I have been assured all of this is covered.
Part of the attraction to buying pre-built is there is no hassle of ordering parts, building a system and having to ship things back and forward if they do not work. Again with this method if it does not work out of box, it will be replaced at no cost.
I recall looking at a nice black and red Corsair PSU that rated well, I can't recall what it was called though.
**EDIT** (It would've been the Corsair HX620 620w)
I was also reviewing the mobo's and the E Pro looked the best, got good ratings and had the best 1-click overclock method.
I've been dicing up between the CM HAF932 and Silverstone Raven RV2, I think I'll go the HAF932 for looks though.