The only other thing you should upgrade is the processor. The one you have (2.0ghz) is bottlenecking your video card and RAM. It would make the game stutter and have lower fps.
Get a new CPU and video card.
Are you sure about that? Because I remember I bought GTA:San Andreas from TRU right off the shelf.
Maybe The Orange Box is just out of stock. Wait for them to restock it.