I would like to pick up a used mtb to occasionally ride with friends. I currently have a Surly Crosscheck cx bike that I commute on and put a fair amount of road miles (125-175 a week). I tried it with some cx 32mm tires at the local mtb ranch. I made it through, but felt like I really needed something smaller and more manurvable on dedicated mtb trails... though a lot of that probably was due to user error! Realistically I would probably only ride it 1-2x a month on trails, so I don't want to spend a bunch of $$. So I'm hoping I can score a decent hardtail at a grarage sale for under $100 ... but would probably be willing to spend 150-200 on some decent quality. Is this realistic? What kind of years/bikes would fit in this range? Oh and I would rather bite the bullet and spend more than settle for someones dept store crap.