Easy hardware questions

Okay, I noticed on overclockers.com that AMD cut prices on their 64-bit line; the price on the 3800+ looks especially nice. This made me consider upgrading my system, but I have two questions: first, what are the popular/best motherboards for AMD 64 systems? Secondly, let's say I buy a Gig (2 x 512mb) of Kingston HyperX RAM for my system. If the motherboard had slots for 3+ sticks of ram (the first two of which would be taken up by the new RAM), would it be beneficial or harmful to put my old 512mb PC3200 Value-RAM in as well?

(I am somewhat behind on my hardware knowledge lately, as I must study for college rather than reading about hardware, so if I am making any great errors please let me know)

 

If you stuck in the value ram it will make all of the ram run at the speed of the slowest stuff. I really dont think 1.5 gigs will be much of an improvement over a single gig and the performance hit wouldnt help either. The Asus A8N boards are very popular, mostly the Deluxe and SLI versions. There are others so just read the reviews on any that look good, newegg always has tons of customer reviews.