256mb or 512 (HD3850)

[Wii]

The 256mb at an amazing price...
http://www.bestbuy.com/site/olspage.jsp?skuId=8636657&type=product&id=1194053242019
The 512mb at a reasonable price...
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102715&Tpk=sapphire%2bHD3850
But what about the performance...?
I want to run FS9 on one but what framerate difference am I going to see on them? I should be able to max FS9 with more than 20FPS right? I can afford both. (256mb is USD$175 w/tax free shipping and the 512mb is USD$205 w/tax and free shipping)
:-/
Been trying to make up my mind forever but I need other opinions to be sure I've got what I've been looking for.
AMD Athlon x2 2.5Ghz
3Gbs RAM
320Gb HD (205 left)
Vista Home Premium
Running FSXD SP2 (on medium low settings no filtering or AA at <20FPS) and FS9 (high settings no filtering or AA no clouds no render to texture 10-30FPS)
The nVidia 6150SE is not doing the job...
No I do not want the 8800 so don't even suggest it.

[machineman9]

What sort of resolution will you be running at?

[Wii]

1680x1050x32 and no intentions on changing it.

[NickN]

512

if this is for FSX you need 512 even without the higher resolution

[markag]

I have to agree with NickN.  512mb is pretty much the standard now a days.  Developers are placing larger and more detailed textures into their games, and the extra video memory really helps and makes a noticeable difference on newer games.  It especially help at higher resolutions.

[Wii]

512mb it is.

Thanks for your help