Because programs are about 20 percent larger with 64 bit systems you don't gain anything if you only have 4G in your machine. If you had 8G ya vista X64 would be the way to go.

I don't think I need more ram for just 5 instances per computer but Ill find out.

I had many problems installing Vista from a win2k upgrade, maybe if I was installing clean it might be different. There is just no compelling reason to move to 64 bit, espically with the advent of SSD. If I move to the server mother boards then ya Ill have to use vista (or server software but vista would be better for home use). But thats in the far future.