Mobo Help..

Alright, now, i have a Dell dimmension 4550, ive upgraded the PSU to a ASUS 430 W i believe (yes i put a whole in the dell dimmension to fit it in, did absoluetely no harm to the comp) and ive upgraded my vid card from some random nvidia card to a, ATI X800 XL 4X/8X 256 MB Card..But ive yet to upgrade my mobo..See its running my graphics card at 4x, and my processor is also 2 ghz..(Pentium 4) and i have 2 sticks of 512 mb i believe buy (PNY?) yeah cheap ram and im getting cheap results....I had ran a MEM test last night, and got like 6-8 errors...so, IVE decided im going to upgrade my mobo and processor and of course ram, and thats where i call on u guys to help, i need a mobo that can hold my graphics card (agp) and then i need advice on a great processor for it, and ram, i need help on which is the right ram to buy, im not talking bout pin numbers and stuff, cause i kno ddr and stuff, i just need advice in what manufacture to buy from and what ram yall would recommend with the mobo u would recommend...Thanks for those who have taken the time to read, I really appreciate it.

 

it would be very much so helpful...