should be pretty easy to pick up a laptop for tuning. Those programs don't require much to run. I'm sure you should be able to get something brand new in the $400-$500 range. I would stay with the better brand names HP, Toshiba, Sony, Samsung maybe. You can get either a AMD or Pentuim processor and either way won't matter for basic computer use. You should be in the 4gb for memory, pretty standard. It may have 2gb if it's a cheap price, but it may have 8gb (which is max for most). I wouldn't worry about hard drive space as external and thumb drives are cheap now. I have a 1.5tb external, and it was only $130. that is TONS of space.
You can search the net for good deals. I got my HP for 25% off with a coupon i found online. But you can try Office depot, Office max, best buy, Fry's, Egghead.com, tigerdirect.com and HP.com or many others.