i dont think i have tried that one, reference yourself to the OCZ1250 on the size, I tried about 5 others besides OCZ1250 to no success what you want to get its a full modular Atx Psu, if your worried about the connections there is nothing special its very standard all the plugs are the same, the only thing different that i noticed on the stock 875psu was that one cable has 1 molex and that was all and the upgraded Psu have 3 molex, other than that everthing fits.
The ocz 1250 watss has a length of 175mm , only 15mm longer than dell stock psu. I checked ans tried and it fita perfectly. But, if u read page 1, and some other threads here, some users claimed they cant use area 51 psu bcouse of the pins for the side window. The answer is no there is no pins on the 875 watt aurora psu. Not sure on the R3 but on the R1 alx there isnt any pins. So if its true the area51 psu has the same physical measurement with aurora psu, it will 100% fits. I believe aurora psu is 160-165 mm length.
And bionil, crossfire of 7970 is cheaper, quieter, performs about the same, , and run way less watt than quad 590s.
Im thinking of selling my 590 and get 2 amd 7970...