Wish I had seen this earlier, get the latest Tsunami case from ThermalTake.
Whatever AMD CPU you get make sure it is unlocked. Older AMD XP2500+ CPU's (within the 40 week of manufacturing) over amazingly, getting from 1.83GHz to 2.2GHz with stock HSF (Heatsink and Fan).
Get urself a nice ThermalTake Volcano Xaser HSF and overclock your CPU by upto 400MHz.
Whatever case you get make it Aluminium(UK)/Aluminum(US), it is a LOT lighter, it will also reduce chasis temperature by a few degrees C.