A radeon 7750 should be a great upgrade for that system, it's quicker than the 6670 while also consuming less power. The 7750 should also work fine with a 300W PSU. Also, the 6670 is far too weak to use that 2GB of VRAM, I'd recommend the GDDR5 version of the 7750.
That i5-2400 is a very capable CPU, so an upgrade to the power supply would give you alot of upgrade options such as getting a higher end video card.
would there be much benefit in getting an upgrade cheaply for the PSU such as http://www.newegg.com/Product/Product.aspx?Item=N82E168...
for 19 after rebate (430w) or am I better spending a little more to create more options? I am also concerned as I am told the Dell motherboards and cases are harder to find good parts for
Thank you so much for the help, what do you think about this as it would keep me close to a $100 and I think I may want to upgrade the pc in two years or so. I think this power supply would also allow me to add an extra Hdd for pics like my wife wants