Dilemma

Hi all, I currently have a Dell Optiplex 380 (oh god it's a Dell, I know). I received a 750W Corsair as a gift and I put it in the PC, no problems so far (4 months now). The situation is complicated so I can't buy a new PC or change the case. however, I can change the internal parts of the PC (its weird, I know, but trust me when I say I can't change the case or build a new PC).

Anyways, I bought a XFX 6870 to put the 750W to good use. It turns out, the CPU heatsink is blocking a part of the PCIE slot. I currently have a 5570 that fits fine and works fine, but I wanted more gaming performance. I have returned the 6870 and am now setting my eyes on a Powercolor 6850, the fastest single slot graphics card I could find. The CPU heatsink doesn't allow me to add in a wide card, any bigger than ~1.2 inches and it won't fit. Length and height are no problem however.

Then I came across an idea...the CPU heatsink part that is preventing me from installing a duo slot GPU is made out of hard plastic. I do have a table saw at home and was thinking I could cut that part off (the plastic extends farther out than the heatsink itself which is why it's blocking the GPU). Then I could buy a 6870 which is cheaper and faster too than the 6850 single slot version (which costs $270 on Amazon).

What do you guys suggest I do? Wait until a 6850 single slot go on sale or cut the heatsink and settle on a cheaper/faster 6870? I was also thinking of replacing the heatsink itself (LGA 775 slot) in favor of a smaller one that might leave me room for a duo slot card, but I'm having trouble finding a decent and small heatsink.