Thank you for all your comments. Very helpful. I feel less scared about 64 now.
I was pondering why no other tight 5 bothered me when I played rugby, (although there was one Welsh Valleys team that I'm glad I only met once), but stuff like this 32/64 caused brain damage. No answer to that.
I will go for 7/64 and 8gig of Ram. I now need to research the best video card to use!