Buying a new bike-Need HELP
 

Whatsup guys, I'm new to this forum and getting back into biking after a long break. I'm buying a new/used bike and can't decide. I already know I need a 17-18 inch frame. I went to a local Trek store and tried out both sizes and they fit fine. I'm finding some nice used bikes on different sites and am not sure what to buy. Here's what I'm looking at so far:

-2004 Specialized Stumpjumper frame with full 2003 XTR components (everything).
-2000 Klein Adroit Pro with also full XTR
-Jamis Komodo Team 18" Fox Float 100RL-Truvative Stylo Team Cranks, Hays Hydrolic Disc Brakes, Mavic UST Tubless Wheels, Shimano XT shifters and derailleurs
-2004 Cannondale f600 (http://www.cannondale.com/bikes/04/cusa/model-4FS6.html ) specs
-GT Zaskar LE Custom w/ XTR, XT, Chris King-XTR V-brakes, XTR rear der, XT cranks, SRAM grip shift, Chris King headset, Rock Shox with speed coils, custom blue and yellow, Azonic riser bar, Note: needs right rear XTR brake arm
-GIANT Iguana (2003) for $400. It's got a Manitou front Fork and disc brakes (Hayes) a wireless computer. I was thinking if that is a good frame, than I wouldn't mind buying that and changing the parts around... I think the parts that are upgraded are all specialized.

My boss is really big into mountain biking and he said to try to buy a newer frame. However, the Specialized is a nice bike. I want to stay under a $1,000. Can somebody help me out? I don't want to buy a crap bike to learn on. I want something nice that will do what I want. Somebody give me a hint, or if they know of any bikes for sale that would suit, please let me know. Do Treks have lifetime warranties on their frames?

Forgot one thing, I would have listed the prices on all of them, but they're auctions, so I have no idea what they'll go for. I do know that the Specialized wants $1,000 and the cannondale wants $700 and the Jamis wants $1,150. Sorry about that

Thanks