Well done you.

I've been biulding my own PC's for about 10 years and they are soooo much more reliable than the factory bought machines.

Word of advice research the motherboard first. Try to get a top of the line motherboard and dont scrimp it will have a lot of features such as Soundchip onboard and improved I/O chips so in performance terms it will be worth the extra cost.

The DVD drive will be used the least so you can save a considerable amount of money and get a cheap drive.

Try to buy from a company that sells OEM Hardware and Software you will save $'s

Finally you havent factored in the cost of the O/S have you ?

I'd give the exact opposite advice. Motherboards today all perform similarly and have similar support/longevity as long as you choose a reputable manufacturer (Asus and Gigabyte being the main two) so you can go cheap. Top-of-the-line ones have features you won't use (obscure RAID modes, OC options you don't need, more PCI-E slots than you can fill).

And you should choose it after the CPU, graphics and RAM, since it doesn't affect performance but you need the slots and sockets to support those three.

Go for a Core i7 machine, they absolutely fly

I'm running Vista 64 on it now and it's already lighting fast, going to put Windows 7 on it next week when I get my MSDN key for it

He said $500 or less. I pushed it to $650 since $500 would be like a quarter of the performance, but the chepest Core i7 system without skimping on the video card is $1200+. And realistically if you're going to spend $150 more on the CPU that money would be better spent on graphics for a gaming PC.

Source for typical builds: http://www.techreport.com/articles.x/17102/6 and http://www.anandtech.com/guides/showdoc.aspx?i=3610&p=7

http://www.anandtech.com/guides/showdoc.aspx?i=3563&p=5

Read whole article.

Amazing (not) how similar my X3 720/4850 suggestion is to the AMD Budget's spec and price.

Oh come off it, I built a Core i7 box 6 months ago for $1500 AUSTRALIAN where everything on the planet costs double. That was with 2 hard drives and a 9800GTX+ too. I could have cut that cost down plenty if I didn't skimp.

I just priced a Corei7 system on NewEgg for $765 which was a Gigabyte Motherboard, 2.6Ghz Core i7, 3 x 1GB DDR3 RAM, 9800GTX+, 400GB HDD, Case w/ 500w Power & DVD Burner. Could easily save more by going for a cheaper video card, single stick memory, smaller HDD.

There you go then. The 9800GTX+ is too weak to be paired with an i7. If you saved $150 (USD) on the CPU by switching to an X3 720 you would see maybe 5-15% difference [compare the i7 920 in games to the X4 720]. If you then spent that $150 upgrading the 9800GTX+ to two 4870 1GBs in CF, you would see DOUBLE framerates. That screams unbalanced, if you had the money you should have spent way more on the GPU rather than the i7. The i7 only makes sense once you have a 4890/GTX275 class GPU.

I'm not denying you can build an i7 system as cheap as I said, just that my system would actually be faster in games due to the extra GPU budget.

I don't use mine for just games though, I use the 2nd hard drive to install OSX86 so I can run Logic Studio. I need the CPU power for that.
Having said that, I've had no trouble at all running any new game on full resolution and high quality graphics. I run Crysis on high, haven't tried anything higher than that, it looks amazing as it is.

I also think a Core i7 PC is more upgradable in the future as it's new tech, the Core2 series is at the end of its development.

It isn't actually; there are no more LGA1366 CPUs on Intel's roadmap for 2010 except the $1000 Extreme Edition Gulftown. Sorry, but your socket is dead. The socket that will last the longest is Socket AM3 which will go to early 2011.