This chart can be used to compare different CPUs, but it doesn't have the AthlonIIx3 435 yet. I used the PhenomII x3 710 to compare to the AthlonII x4 620. You may want to plug different CPUs in and compare them to what you want to use the PC for. http://www.anandtech.com/bench/default.aspx?p=84&p2=106
Also make sure you check different CPUs out for combo deals. This deal with the PhenomII x3 710 knocks $20 off the price of your choice in RAM, dropping the 710 below the price of the 435.
The hard drive is an older, slower hard drive, but at the price it's hard to pass up. In terms of the CPU, i'd probably take the $25 you saved on the combo deals and go for the PhenomII x3 720 BE and same RAM for $194.
Wanted to update that it all got assembled yesterday and POSTed the first try!
I also successfully unlocked the 4th core on the Phenom x3 720BE and ran it on a Prime95 blend test for an hour, so I got a good one! It was very easy to do on this motherboard. I did change it back to the tri-core as I don't really need the extra core at this point.
The RAM auto-detected at CAS 9-9-9-24, but a quick change to the BIOS and it is 8-8-8-21 where it should be.