Decent Brakes

Decent Fork

or:Fork & Free Headset

Did you mention your drivetrain is 7-speed??

I'm going to go against what everyone is saying here. I think for the $300 you're going to spend upgrading your 7 year old bike, you'd be better off buying one of the two new bikes you've listed.

I'd spend as little as possible on your current bike, keep it as your spare and use your new one. It'll come stock with vee-brakes, a 9-speed system and a fork that is equal in quality to the one you currently have.

Now, my first recommendation would be for you keep your existing bike and save up another $150-$200 and buy a slightly better bike. Bikes in the $500 range will have much better components and a decent fork.

L8R