How much is my CPU going to drag me down?

Get a Athlon 64 X2 4200+ Socket 939 if you can, there is still stock for some region...then you probably only need to spend less than USD90...

I can buy an AM2CPU board, so I can use AM2 processors and DDR2 RAM. I was thinking about getting that, then either a 4400+ or 4800+ Brisbane. Do I need the 4800+, or will the 4400+ do the job?

Also, I don't plan on OCing the CPU.

I'd upgrade your RAM first (from 1 Gig to 2). Then upgrade the processor to either an X2 or Opteron dual-core.

-Wolf sends

For $175, I can get:

AMD 4600+ AM2
2GB DDR800 RAM
AM2CPU Board

For $160, I can get:
AMD 4400+ 939
1GB DDR400 RAM

Overall, my computer will end up the same, but if I use the AM2 board, it will probably be easier to upgrade in the future.

Is it worth the $15?

I think you meant:

For $160, I can get:
AMD 4400+ s939
1GB DDR400 RAM

If this is the case, then I would say, no. It's not worth it. I've been running just fine with my rig (see specs below). I've heard some unpleasant things about the AM2CPU board (like it sits loose) and I'm not sure just how upgradeable it is. Can you put an AM2 5200+ in there?

-Wolf sends

i would strongly recommend

AMD 4600+ AM2
2GB DDR800 RAM
AM2CPU Board

i recently upgraded from my skt939, 3200+ venice, 1 gig 400 dual channel to am2, 5600+, 2gig 800 dual channel and it has made an unexpectedly big difference for gaming even though i still have me ole 6600GT. on WoW i get about or not quite twice the fps @ 1024x768 with max candy settings. on Insurgency (a source mod) i get atleast 3 or 4 times the fps @ 1024x768 with max candy and 20 players because it's known to be a very cpu intensive game when more people join. on the source engine in general the performance between medium and high textures has been massivly reduced. before the new rig i used to get unplayable fps spikes with high textures. played portal last night and dam lol was getting crap but playable fps @ 1024x768 with lowest candy. i need a new gfx card :-(

i believe every am2 board supports every am2 cpu? my mobo couldn't recognize my cpu till i flashed the bios now its fine. also with an am2 board you can upgrade to the upcoming phenom quadcore cpus but keep in mind you can't use some upcoming features such as shutting down the other 3 cores when your only using 1 to save power.

i also found out the venice is a good overclocker after i bought my new rig and i noticed your only getting a 4600+ so overclocking your current cpu is also a good solution and probably a better one in my opinion. oh and if you do end up overclocking i recommend you buy some arctic silver 5 cause its cheap and it should lower you cpu temp by atleast 10 degrees celcius.