I've always had good experiences with Cybermind but i'm sure there are others too ( fuwell, video pro etc) Most of there stuff is at least 1 year warranty. They can supply OEM XP pro too.
I wouldn;t go to their FUnan outlet as they just supply what they have in stock. The Sim lim tower place has stock of pretty much anything you might want.
I prefer a good casing and power supply as this usually see me through 3 to 4 years . Currently using lanbox light and very pleased.
Stick with brand names if you can, as they will have local warranty and support. Asus is the only mother board i'll use. very reliable. Kingston memory ( 2 gig as xp cant properely use 4 gig anyway) Seagate hard disk and then rest of the budget to get the fastest processor you can. I find higher spoeed processors to be overrated. Your money is much better spent on a reasonable video card. You might struggle with 1500 bucks but it shouldn't be too far above for a decent rig.
There's a lot of fancy stuff out there to temp those last dollars out of your wallet
Cheers