If cheap, reliable, and street legal is what you are looking for, check out KDX200 or KDX220. I only trail ride. I have had full blown motocross bikes, motocross bikes set up for trails, KTM purpose built trail bikes, and now a KDX220. The KDX gives the best bang for buck IMO. It can be mild mannered to putt around with the kids or it can scream. Perfect for gnarley single track to. If I could afford a 2008+ KTM 300 I would rather have one, but like you, I was looking in the under $2k range when I picked it up. Mine is heavily modded. Has KX125 front end, suspension sprung and valved, cylinder ported, milled head, bored carb, woods pipe, and a heavier flywheel weight(they already have relatively heavy FWW stock), I can almost come to a complete stop without clutch and it won't stall. It still isn't the fastest or most powerful bike, but when riding in the woods you can only go so fast. It will run with any bike on the trails I ride.

You can pick them up for $1000-$1500 stock. Half the ones I've seen have already been titled. For under $500 you can send your top end to Jeff Fredette and have it ported, head milled, and carb modded. Really wakes them up. He has won numerous ISDE titles on KDX's, so they can hold their own.