Choice for computer components

Hi everyone. I'm going to be building a second computer for internet use and some experimenting with video editing programs before I actually load them on my higher end P4 computer that I also do not go online with. I have three questions if I may .....

I'm thinking AMD because it seems less expensive. The board I'm looking at is an ASUS A8N-VM-CSM that has both integral video and sound. Its really all I need. It also has firewire so that is a plus. If anyone knows anything very bad about this choice I'd love to hear it.

My second question is regarding the processor. I was thinking about the AMD Athlon 64 3000+ chip. My question is, Is there any advantage to the 64 bit if I don't use XP 64 or am I wasting money here?

Also, the old timer computer that I'm replacing happens to be running a VIA Apollo Pro chipset that supported DDR way back when .... LOL I have 2 -256 meg chips of DDR 2100 memory. My question is not really being familiar with the AMD platform .... I remember reading somewhere that "unlike" Intel, the AMD cpu runs independant of memory timing and speed. Will these DDR2100 chips be ok in this thing or should I not chance it and get a few DDR3200 chips?

Thanks much!

dcp