that 20 A rating better be continuous current, not max. you need at least 18 A on the +12v rail.
i'd keep the 6670 running at stock settings because the psu amperage is marginal (the oc card will use more power). the stock 6670 1gb gdr5 will be a good upgrade over the gt 240 ddr3 anyway.
Not really. The closest would be the 9800GT which is slightly slower than a DDR5 HD6670 but that card is several generations old and DX10. Nvidia doesn't really make any low end cards that are comparable in price/performance to AMD.
nvidia doesn't have any new gfx card that delivers 6670 level and price. 6670 is the most powerful gfx card not requiring any pcie connector.
@pherule: the 7850 will not be compatible with his current system. not to mention cpu bottleneck.
That's unlikely IMO and even if so there's still no way it is going to run on a 300w PSU. Even ignoring that it will cost well over double what the cards this guy is talk about cost. It's simply doesn't make any sense for this situation.
The 7000 series should run with lower power requirements on average, so I expect the 7850 to require less power than the 6850.
the 6850 has 127 w tdp. amd set their new 7970 with 250w tdp, similar to their previous single gpu flagship 6970. if the new 7850 has 127~ tdp, it will not fit into OP's machine...unless it uses around 60-65 w power.
wait for the 7850 to come out and match the numbers then.
OP's cpu will also cause bottleneck to the 7850 in resolutions ranging from 1280x720 to 1920x1080.
edit: amd has set msrp for 7670 at over $179 at launch. compare that to 6670. http://www.techpowerup.com/156312/AMD-Radeon-HD-7000-Se...
the amd hd 6670 have an dx 11 and it will be the best with that psu of 400w and its minimum requirments is also 400w psu so u should choose that graphic card or hd 6570 but i should go with hd 6670.and if u have an 450w psu u should go with hd 6770 or 6570.
u should use hd 6670 will be the best answer or hd 6750 the ati hd 6770 will be riskier de5-roy is right so i must say that u should use hd 6670 or hd 6750 the hd 6670 is more powerful and better for gaming than the hd 6570 so i will recommend u to get an hd 6670 it is good for ur psu and risk free.and if u want an good graphic card u should change ur psu to minimum 600-700w.