It would be nice if you could measure the distance between processor heatsink (processor cooler) and back panel, otherwise I have to follow Optiplex 745 measurements, however it is looks like you have a bit more room, for now you are in between GTX 550TI and AMD 7770 at most, judging by money, however, I missed one more thing, what is your form factor, is it mini tower, small firm factor, desktop or ultra small form factor? I will try to find pictures? And what is your power supply wattage?