you sound like you're in a similar scenario to what i was. tried mountain biking when i lived with a friend who biked. i rode his old (2002?) diamondback hardtail. shitty fork, only front disc brake, etc, but for singletrack, it worked fine, and i had a ton of fun. i spent 700 and got basically a step down from an xc race bike on a good closeout deal from a local shop. basically all solid compenents except for the fork. i found a better for on craigslist (32 float rlc for $250, not sure why the idiot sold it that cheap...) and that made a huge difference on the bike. i rode that for about two years until i started riding more aggressively and breaking things regularly.
then i found a trek remedy (5.5" full suspension freeride frame) on craigslist for like $500. swapped parts over to that and it was like a whole new world. drops that were sketch on the hard tail turned into super fun features on the full suspension bike. it was like freeride skiing's summer cousin. long story short, i snapped the remedy frame, trek and my local shop hooked it up big time with the warranty, and i now have a $3500 bike that i've spent maybe $1500 putting together, but i can ride it at diablo, launch (spring mtn, pa's new bike park), rode it at blue last summer, and it's light enough that it's fun for xc rides, but burly enough that i'm not gonna be going through minor repairs all the time like i was with the hard tail.
sorry for the rant... if you want to bike like you ski, you're probably gonna want to look for something with at least 4" of travel front and rear, which will allow you to hit jumps and drops without totally wrecking your bike and your spine. it's getting close to the end of bike season in PA/NJ, so you should be able to find some closeouts sitting around. not sure where in NJ you are, but if you get down to the philly area at all, there's a few great shops here who i'd be happy to point you to.