GTS 450 2GB DDR3 vs HD 6670 1GB GDDR5

But 450 has 2Gigs of memory and 6670 only 1Gigs

1. The GTS450 is a couple of tiers higher than the HD6670, but the chart does not indicate it's a GDDR5 version. If it is, then having DDR3 instead may bring it down to about the same level.
2. At your resolution, the difference in amount memory will make no difference.
3. The HD6670 uses less power. If your PSU is not a good one (e.g. Seasonic, Antec, or Corsair), it may not be enough for the GTS450. What brand and model is it?

Its Codegen

http://www.codegenworld.com/showDetails.asp?max_id_sear...

Ouch, I would not trust it to power a GTS450. Does it even have a PCIE power connector on it? Hopefully it is enough for the HD6670, which does not need one.

Yes it has one 3x2,
Ill go with 6670 then...

That sounds like a good idea; much safer anyway.