Project : Vista

I have two large decisions to make. Do I get the 32bit or 64bit versions of Vista and do I upgrade my PC or leave it as it is? I know that i'll be getting the Home Premium version but that's all! I currently use Windows XP x64 so i'm tempted to use get the 64bit version, but will it work? Is there enough software available? Also, can my hardware support it? My machines current spec is a 3.2Ghz AMD Athlon (single core) with 2.5Gb of RAM and a 256Mb Radeon X1300 graphics card. I can't help but think it's not going to be powerful enough! Any help would be appreciated so feel free to leave suggestions using the comments system.