DDR3 RAM makes more sense as there are few boards that support DDR2 and those that do are very old.
Get an Intel Core i5 or AMD Phenom II X4 processor.
Go for gold and get a card with 1GB or GDDR5 Ram. Again anything less is old tech.
As for the PSU, I would personally recommend a reputable brand OCZ (formerly Computer Power) Ultra or Corsair. If you can afford it get a 700-850Watt. Future proof ur purchase as much as possible.
New Eggs prices are tough to beat and Tiger Direct has a wider selection