Just casually looking over the parts.. I'd personally suggest an SSD X-25 or OCZ 32GB min. The 1TB drive you have listed will probably get around 100MB/s or so. Wtih the SSD's its possible 200+. I don't have any personal knowledge I can give you on SSD's as I am a little too poor to get one of those right now but from my understanding of computers that spindle drive will be one of your bottlenecks.
Also the 5870 in my opinion is a little overboard. But hey it isn't my system
the 1200 case is pretty nice If I was going to completely build a brand new system ground up I'd defiantly choose the 800 / 1200 This is the case I have right now which is pretty stout
http://www.thermaltakeusa.com/product.aspx?c=1309&ID=1412 The only downfall being on that case is the rad piping is 1/4" but the pump and everything else is 3/8" So you don't really get the benefit of 3/8" With a Pentium D 940 my temps are around 86 F with system at 89 F at idle right now. Playing games it gets up to around 110 F.
One other suggestion I would quickly make if you can it would be a great help is to link to the individual components.
Also for the memory. Since you have 6 slots and it being triple channel. Correct me if I am wrong any one but wouldn't it be better to fill all the slots? like instead of 3x2gb get 6x1gb? like 2 sets of these?
http://www.newegg.com/Product/Product.aspx?Item=N82E16820104121 If price is of concern which with the added 5870 it doesn't appear to be it is then I'd suggest 2x of
http://www.newegg.com/Product/Product.aspx?Item=N82E16820104115
One other thing I am sure this will be an I7 but which one?
But defiantly if this guy has this much to lay down on a system and wants good performance. SSD!!!!!!! Can't put enough ! seriously from everything I have read about them. I desperately want one.
I'd suggest this one at min.
http://www.newegg.com/Product/Product.aspx?Item=N82E16820220455
This one if you want to spend a little more.
http://www.newegg.com/Product/Product.aspx?Item=N82E16820167013 it being slc it should last a little longer than mlc but the price... ouch.
And finally this one. If I was rich. I'd have one or 2 of these *drools..
http://www.newegg.com/Product/Product.aspx?Item=N82E16820227499
Performance
Sequential Access - Read up to 870MB/s
Sequential Access - Write up to 780MB/s
Just imagine.. With that I can say with almost certainty that the HDD would either no longer be a bottleneck or defiantly not as big as one.