When I built my new computer last year, I went with an Intel Motherboard and a 1.7 Ghz Celeron. I have a 64Mb AGP video card, and a Philips Quad sound card. Running 512Mb of DDR memory, I have no issues with the online gaming I do. Granted, I'm running the 2D client and not the 3D, but I have had no problems using a Celeron.

SD Ram and DDR memory are not interchangeable as I recall.

When I built the new computer, I had planned on recycling some of the old parts to the new machine, but found that many of them would not carry over. Memory is getting cheap; just count on getting newer, faster memory. If you switch over to an AGP video card, be certain the level of AGP is compatible with the motherboard. The first video card I selected was not supported by my MB, and it would have damaged it to try and run it. Fortunately, Tiger Direct is pretty good at doing exchanges, so I simply called them, got an RA number, and sent it back with an order for one that would work.

My case and power supply were also no longer compatible with the new MB. The new ATX boards have an auxilary power supply connection that my old system did not have. I ended up picking up a new case and supply on sale from CompUSA from just a bit more than a power supply alone.

My sound card SHOULD have worked on the new system, except that when I upgraded, I also upgraded to Win XP, and the old card (a very good one from Turtle Beach) did not have drivers for XP, nor were any available.

Upgrading computers is a lot like working on cars. Start with your estimate, and then double it, and add a bit more for a buffer. Something unexpected is going to come up in the process for certain.