Another video editing question. Opinions please.

[ddeder]

I am planning to build a computer that I would like to use for home video editing. Here are some of the components I plan to use:

EP-8K7A mobo
1.33 or 1.4 GHz Athlon
256 MB DDRDRAM

Now for the video card...

What differences would I see between using a

ATI Radeon 32MB DDR 4X AGP (~$70)

and using a

Leadtek Geforce3 64MB DDR with TV / DVI out 4ns 4X AGP (~$340)

or a

Guillemot Hercules 3D Prophet III Geforce3 64MB (~$420)

Also, is 256 MB of RAM sufficient? Would I see better results with more RAM?

Thank you for any replies.