Galaxy makes a low profile, low power 9600GT that I picked up at best buy on close out. It is a half height card, but is quite long and barely fits in my mid-tower case. Depending on the orientation, it might fit a small form factor case because it is half height. It is slightly undervolted and underclocked, but seems to perform well.
It uses about the same power as a HD4670 and I am running on a generic 300watt power supply, without problems except for one crash which I am not sure was power related.
However, a 220 watt power supply is quite a bit weaker. You might have problems with anything more powerful than a HD4550 or HD4350. These should be adequate for watching video though, even Blue Ray.
As for you requirements for ddr3, the 4670 and 9600GT that I described are DDR3, but only 512mb. However any card that will work with your power supply wont be able to utilize more that 512mb of memory anyway.