Mountain Biking - Need advice buying my first MTB - help out a noob please!

Ok, so it's been a few years (about 10) since I've been on a mountain bike. I'm in need of a low-impact (thanks to my knees) training regimine to shed some unwanted poundage I gained after being discharged from the Marine Corps. I have been reading in here for some time, and visiting my LBSs, and have come across what appears to be a fantastic deal, and I want the experts' opinions (you guys) on what I should do.

My initial budget was around $350, but after researching a bit I realized that about $500+ would get me a bike I can really ride hard, especially since I'm 260 lbs at the moment. So I started looking at some more expensive bikes with better components and materials. Then today I found a 2006 Specialized Rockhopper Comp Disc, 21", that is listed at the store for $799. I inquired aboout it and the guy told me that a couple weeks ago a married couple came in and wanted a different brake setup on the bikes they were buying, and so they took the brakes off of this Rockhopper and put them on something else. Then, the bike shop decided to put a set of Hayes HFX-9 hydraulic brakes onto this Rockhopper, and they did not increase the price (still $799).

I got to talking to him and learned that he is also a former Marine (Semper Fi!), and he offered me a Devil Dog special deal. He said he would let me have this bike, with the upgraded brakes, for $650. Now I researched a while and found that generally those brakes are about $150 each, adding about $300 to the bike.

So this is my question - is this a deal that I would be crazy to let go? I really would love to stay in the $500 range, but for a extra $150+tax this seems like a great bike! Talk to me...

The Rockhopper is a great bike that will serve you well for a long time. However, before you commit to this bike (or any bike for that matter), you should see if the bike feels right to you.

If you want to stay closer to your budget then look at the base Rockhopper (if you can find one) or the Specialized Hard Rock model that is closer in price to what you're looking for. I like the Konas and I think in your price point you'll find the Kona Blast to be a pretty good bike. Gary Fischer also makes bikes that you may like.

The key is to try the bikes and see if they feel right to you. If you feel you're stretching beyond your budget, don't worry because at $500 you'll get a pretty decent entry-level bike that will suit your needs fine.

If the bike fits, then $650 is a good deal for that bike!

I'd say "Go for it".

The Rockhopper is a great bike that will serve you well for a long time. However, before you commit to this bike (or any bike for that matter), you should see if the bike feels right to you.

If you want to stay closer to your budget then look at the base Rockhopper (if you can find one) or the Specialized Hard Rock model that is closer in price to what you're looking for. I like the Konas and I think in your price point you'll find the Kona Blast to be a pretty good bike. Gary Fischer also makes bikes that you may like.

The key is to try the bikes and see if they feel right to you. If you feel you're stretching beyond your budget, don't worry because at $500 you'll get a pretty decent entry-level bike that will suit your needs fine.
So assuming the bike does feel good and fit me well, this is a good financial deal?

You can find Hayes on closeout for about $150 a pair, but still even at that it's still a good deal for that bike.