2 gigs of RAM would probably be ideal for vista on a 32bit OS, mostly on a budget. I think the stores you listed will be the best places to find a laptop like that.
Just to note, the "Pentium Dual Cores"...if I remember correctly, they are in fact Core 2 Duo architecture, just with a lot of hacked off cache and things like that. Nobody quote me on this though
They should probably perform about the same as Turions, methinks.