Spend the $500 on a laptop, and I'm confident you'll be able to snag something with 6-8gb of RAM and a decent processor.
My girlfriends laptop cost her ~€400 and it runs the sims 3, has 8GB of RAM and a somewhat decent processor.
Of course, you could cheat like I do, and find somebody who owns a business so they can claim the VAT back off the laptop. (got a laptop worth €750 for €600)
Only it wasn't really cheating because it's my fathers business and I do work there and do actually use the laptop for work related stuff, but that's barely ever.