okay... i've been building my own systems for 7 years now (never bought a box, always built them myself), so i know a thing or two...
1) almost any motherboard with a PCI express 16x slot will be ok. more expensive boards have more options (more SATA ports or USB ports), and usually have better overclocking features; but if you don't need that then a budget board is alright. good quality brands are asus, MSI, gigabyte, epox, and DFI. intel branded boards are also good (although they are made by MSI, so if you buy an MSI board you get the same quality but at a lower price since intel usually charges a premium).
2) AMD and intel are more or less equal in performance at this point. the higher-end intel chips are faster than the fastest AMD ones, but at normal price levels (say, 200 bucks or so) the difference is small. i have an AMD, but would buy an intel right now due to better overclocking capabilities... but for even $150 you can buy a good AMD athlon64 X2 or intel Core2 duo dual-core CPU. just make sure the CPU fits into the motherboard you bought.
3) the X1600 was a decent midrange card a while ago, but it won't let you run the latest games in high resolution with all the eye candy turned on.
a small reference guide:
- ATi usually name their cards like so, from low to high end: x200, x500, x600, x800, x900, x950. replace the x wit a number and you get the generation of the card. thus a 1950 is an older high end card, and a 2600 is a newer midrange card.
- nvidia do the same, from low to high: x200, x600, x800. so a 6600 is a midrange card of the sixth geforce generation, while an 8800 is a high ender of the 8th generation.
4) for windows XP you will also need 1GB of RAM, and for vista twice that. most motherboards right now support DDR2 memory (pretty cheap at the moment), but some use a different type, so check before you buy. it will tell you which type it is in the manual.
5) read an online review (or two or three) before buying anything. they're only a mouse click away and can save you a lot of money.
good places to start include:
http://www.anandtech.com/
http://www.xbitlabs.com/
http://www.hardocp.com/
finally, remember that a new board+CPU "might" require a new power supply unit (PSU). get a good quality one as it helps increase stability and reliability of your system, don't bother with $20 ones. a PSU is something you only buy once every two or three years, so don't be afraid to spend an extra buck on a good one.
if yo have any more questions please ask; but be patient as i don't have the time to go online every day (stupid work lol).
