Will Dell inspiron 531 run ati radeon 4670?

I have a 1 & 1/2 year old dell inspiron 531 with AMD athlon 64 x2dual core processor 4000+ 210 ghz, 1gb ram, 32 bit operating system, and i think 300 watt power supply. I know this isnt a gaming computer but i was wondering if by putting a decent graphics card in it i could play medium to higher level games, but first i need to know if the graphics card will work in my pc. If so should i get the 512mb or 1gb? thanks.

But many forums say the 4670 will run on power supplys as low as 250, and that 300 would work. I dont know though.

Dell power supplies are good units with plenty of juice where it is needed and we have had plenty of Dell owners with similar-and the same-spec as you asking the same question.
And they get the same anwser: It will be fine.
If you are in doubt, go for the HD4650, but try to find GDDR3 versions, they are faster than the GDDR2 units.