as you noticed in my sig, my mobo is a pos oc'er. the 3200+ can only go to 230 HTT before failing so I don't think I can OC that much. A 4200+ cost too much for negligible increase in performance so i'll just get a x2 3800+.
I'd be interested to know how a dual core would benefit you over a single core. I also have a single core (3500 venice) and I'm not sure whether to upgrade to a dual core. Because of my motherboard (asus a8n-vm) I'm only able to o/c motherboard to 219mhz (from 200) - it doesn't have facility to increase voltage.