I'll be upgrading my aging E6600 conroe system soon, and the new Athlon Propus 620 quad core has caught my eye, as has the unlockable Phenom II x2 550. A quad core for $100 isnt bad, no matter how you slice it. What I'm stuck on though, it whether to get an AM2+ board that supports DDR2 memory, or an AM3 board that supports DDR3. Note that these are both AM3 chips. I'm a little open on the price, but I do have to pay for a wedding, so I can't go crazy. That's why I'm considering the AM2+/DDR2 board: it will let me reuse memory that I currently own, instead of having to purchase more.

I use the system typically for development, and some light gaming. I'll normally have 2 or 3 VM's running, along with 1 or 2 instances of visual studio, plus all the ancillary programs that go along with programming. 

What I want to know is: will selecting the AM3/DDR3 board provide a noticeable speedup in application execution (launch time doesn't matter to me) over the AM2+/DDR2 setup, given that everything else in the system is being held constant except socket and memory type?