Later cars have the VVT head, and optimized manifolds among other things.
Erica, for reference my friend just bought a mint 2001 special edition with all the factory add-ons, ~90k miles, and a box of replacement parts like timing belt, water pump, etc. for $9,000 no negotiation. I think with a level head and some negotiation, you should be able to find the "right" '99 for $6,000. Good luck.