Depends on the monitor resoloution but do not expect miracles from the card.
Please do n't double post, it makes it hard for us to follow what is going on.
On a 720 TV you should see good framerates with CoD because it is not particularly hard on the system but not for more demanding games.
I find the two biggest losses in speed are due to AA and shadows with texture and shader detail having less of an effect, particularly at low resoloutions (like 720 TV).
Most newer video cards require at least 2.6 ghz to run without being bottlenecked..
That's a 2.6 ghz Core 2 or equivalent cpu....
An athlon 64 x2 4400+ at 2.6 ghz is still going to be lacking. Even if you got it up to 3.6 ghz, a stock phenom II or Core 2/i7 would still kick the pants off it. On the other hand, that magic 2.6 ghz figure is referring to high end graphics cards (4870/gtx 260 and up), not the 4670. Overclocking would still give you better performance, so give it a shot. Like coozie said, just don't expect miracles.