Do you want to stay the
AMD route, or go with a more stable
INTEL solution?
If you have $400.00 to spend, and plan on keeping your other components, here is what I recommend, at under your budget
The 1.6A Intel Pentium 4 should overclock to 2.13 Ghz (133 fsb) with ease (and with the stock heatsink as well)
The Corsair XMS PC 2400 memory is spec'd up to 150 FSB (300 Mhz DDR). The XMS PC2700 stuff is spec'd to 166 FSB (333 Mhz DDR), but will cost a few more pretty pennies
A02213 CORSAIR CM64SD256-2400C2 32X64 XMS2400 256MB CAS2 DDR DIMM Detail Specs $105.60
A15943 ASUS P4B266-C INTEL 845 CHIPSET ULTRA ATA100 ATX FORM FACTOR 1xAGP(4X)/6xPCI/1xCNR/2xDDR (BULK PAK) Detail Specs (CPU TYPE:INTEL PENTIUM 4 - 478PIN) $115.00
A03080 INTEL PENTIUM 4 1.6A GHZ (BX80532PC1600D) W/512K CACHE 400FSB 478-PIN RETAILED (3 YEARS WARRANTY) $150.00
Sub Total $370.60