Icono, here's something for you...
http://www.newegg.com/Product/Product.aspx?Item=N82E16813185083
that's about 45 maybe 55 with shipping. It's just a cheapo, but pair that up with maybe even a dual core sempron, if that board supports it....which is 50, 2 gb ddr2 for 40.
so 150, plus say 40 bucks for like a 2400 pro and maybe pick up a new psu. For say 300 reusing your old case and drives you could have a decent rig. However, there is a HUGE difference between a sata drive and an IDE drive for performance. I know because I upgraded here last Christmas, had always had IDE drives before....dude, it is a difference. If you can afford it, I'd personally go and get a good board with some overclocking options, good reliable power supply, then whatever else you need to make that puppy work. But you get a good board and PSU, you can always add the other stuff as you go.