Go ahead and get a 300 watt power supply. More drives is more juice, the price difference doesn't justify getting less than 300.
Is the video card agp or pci? I've heard of folks with problems getting known-working pci video cards to work on Athlon boards. There's a setting in the A7V bios to look for a pci video card instead of agp, but you'd have a helluva time changing that setting with no video (use the force, my son
).
Everything else should be fine.
Xayd