Considering your needs, this is what i would build if in your shoes. It would knock socks off the 4600 system. It's a similar price too.
I found an interesting quote that said you need to buy higher than DDR6400 RAM to get the most out of an AM2 processor. Not sure about the truth in that but you might want to check.
Processor:
Here (Read
http://www.pcguide.com/vb/showthread.php?t=49423)
Motherboard:
Here (Good one Vital to system stability)
RAM:
Here (Budget, but good quality chips so should be stable, and cheap)
Graphics:
Here (Cheap, dedicated memory)
Hard Drives:
Couple of these to RAID 1 for server redundancy 16mb cache high bandwidth
PSU:
Here (one of the most important parts for a machine thats on all time)
Case: Up to you... As is the rest.
At the moment Chris, AMD can't touch Intel for processor performance. You do not even need to overclock the E6400 for it to win hands down against the AM2. Why do i suggest things i buy? Because i spend hours_upon_hours_upon_hours researching particular components to ensure i'm not buying rubbish. That is, in essence, why i didnt get an AM2 system this week and went Core 2 Duo when a year ago i swore blind i wouldn't touch intel again after my last rig.
Obvisouly you can chop and change parts in my spec, but its just a rough idea. I could probably find a better motherboard there but i want to have my breakfast. If you can find one on the 965 chipset that would be best as its on a par/bit better than the nForce 680 chip. These two are the best availiable, just unsure how cheap you can pick a decent one up for.
Budget DX10 cards are released in march, btw