HP DC7900 Small Form Factor - Low Profile Video Card



I am getting a video card for my HP DC7900 Small Form Factor Desktop. The specs are as follows:

Core 2 Duo E8400 3.0 Ghz processor
6 GB DDR2 6400 RAM
240 W PSU
Accommodates low profile cards only
Graphics slots support 35W cards (as stated on HP website)
2nd PCIe x16 slot functions electrically as x4

I am looking for the best video card this PSU and motherboard can handle.

Anyone know if I could put a 6670 in there? http://www.newegg.com/Product/Product.aspx?Item=N82E16814161397

If so, would it be bottlenecked by any of the other components?

Anyone have any experience with the 6570? http://www.newegg.com/Product/Product.aspx?Item=N82E16814102942