I see that you put this question/request to "The Hatter" here, but you are definitely (IMHO) not "hijacking" this post. I believe this is a very relevent topic, in fact I think a new should be created to let everyone know that you can SAVE BIG $$$ building your own Mac Hak Pro. I really wouldn't call it a "Hak" as it should really be called a PC/Mac Pro. All you're really doing is getting the right PC parts (which are compatible for Mac OS X) then purchasing the parts and building it yourself.
Now about you considering possibly selilng your current system and building a PC. You can do that and STILL run Mac OS X 10.7 ON a PC, and if you become a (free) registered user on www.tonymacx86.com here:
http://www.tonymacx86.com/ucp.php?mode=register&sid=b1dd0c793f39b3fae3cd2d5257c4 3de6
and read the forums, people like yourself went through the very same issues that you have (as anyone would have with a propritary system like a Mac Pro) and found solutions here at half the cost or even one third the cost and loving their new PC/Mac Pro Builds. Here's one post for example that is talking about the very issues of the GTX 4XX / 5XX card series:
http://www.tonymacx86.com/viewtopic.php?f=15&t=23127
If you can't access it, it's because you need to register first then you'll have access to it. I'm a member so I don't know it you'll have that access or not since I'm already signed on. I know it's too late (since you have your 580 card already), but the GTX 480 is just as good and faster as ANY styled GTX 580. Just watch this vid and you'll see why:
http://www.youtube.com/watch?v=nMM6q7yWcFg
If you want to skip most of the video (you can but I would watch the whole thing) you can go to min marker 5:00 min. and see the difference when you water cool the GPU. You cut the heat load almost in half and it runs just as cool and even faster than a 580 when you OC the 480 to it's max of (875MHz @ 53C under continuos load). But of course water cooling is another topic altogether, but completely worth the effort and you'll have a screaming machine.
You know, everything is work, no matter how you look at it. I really hope others out there start to catch on that they can use their existing Mac Pros while they build they're own Hackintosh on the side and have fun while doing it. It's no different than building a model toy car. And you have a teen that has put together his/her own PCs, have him/her do it for you and when they're done and you're done installing all the files needed to install Lion 10.7 then you can give him/her your old Mac Pro.
Anyway I hope this helps and gives you some hope Chris Witt... Later... 🙂