Open Question: How much would it be to adequately upgrade my computer?

My specs are: Windows Vista 32 bit 3 gb RAM amd athlon tm 64 x2 dual core processor 4800+ 2.5 ghz Polaroid Monitor 12x15 (an estimate), not hd ATI Radeon HD 4670 List the upgrades I should get, the amount for each, the total, and if possible the places to buy them. I'm a gamer and I can run the latest games on the highest settings with smooth running but I wouldn't mind an upgrade. If I need to list more specs, ask. Thanks for your time. My hd is 250 gbs.