5550 are faster than 4650. but the 2GB of RAM for such a card are not really useful. even if the extra RAM will benefit at high resolution or to crank up the setting that use more memory such as AA and AF i don't think the card have enough raw power to process more complex calculation needed when high level AA or AF was applied. eventually even 1GB of RAM is quite a waste but normally most low-end and mid-range ATI now come with 1GB memory. in short if you can find 5550 with 1GB memory i think it will be a better buy