You got a 690, so I'm guessing HP isn't an issue.
I like the CR250's 2000-2001 with the mechanical power valve, IIRC 2002 on has the electronic valves, and it's harder to adjust. Even with a Gnarly pipe and a de-tuned powervalve, CR's have LOTs of wheel spin. I love the CR on the track and in the wide open desert(great in the sand).
KTM200, Pure bliss, and the KTM 2 strokes sell for less than same year Jap bikes. I had a 2003 KTM 200SX, I bought for $1500 with a new top end. It was 6 speed, more grunt than a 125 and it was a really manageable trail bike. It also had twin chamber front forks, I was 40 lbs heavier than the suspension was set for and it was really plush with no bottoming on a small double. If I see another young one for a good price this winter, I'll drop for it. If I could only have one smoker, it would be a KTM 200, even over a KTM300. If I need More HP(smooth trail power) and a plate, I'll ride the 525EXC(only reason over a KTM300 is MPG when riding longer loops)
A little cheaper, a 2000 YZ250, oh ya. Just over $1000, add a 13+oz flyweight, and have fun.
You said also to connect trails, so you'll get a plate? With a plate, don't skip looking at a KTM 400/450/525 MXC/EXC, 2000 - 2002, some will fall in your budget, and I think spending a little bit more on a KTM 400 would be worth it. I just passed on a 2001 KTM 400MXC for $1600, it was a young bike, but the kick stand and kick start vibbed off, he would flex in price so I left. A guy 30 minutes later bought it. I made a mistake on that one, even though I really want the EXC tranny.
I have seen some 2004 250SX's for $1500, and the 2 strokes I've had, the KTM bottom ends last a long time vs a CR.
Lots discount the 2 smoker 125, for me, I can point a 125, nail the throttle and handle a tough section, the power isn't as fierce as a 250, and I can work my line, and worry less on throttle and clutch control. 125's are a blast. For me, the 125's burn down a piston faster than a 250, so slightly higher maintenance
than a 250, and KTM pistons cost more than one for a CR or YZ.
I say skip the KDX, go modern, like your 690(I'm jealous)
Let us know what shakes out