The 4830 works great, amount of videoram is not critical in AH or most games. A lower end graphics card will not benefit from 1G ram at all.
I got a 4830 for my sons gaming computer, overclocked it with automatic tool that came with the card and so far all the games I've tried on it run flawlessly. I haven't benchmarked it but basically all the titles that I play with a 4870 run with 4830 oc at comparable settings and playably. Only for $130 less.
