If you're riding dirt logging roads (some double track I would assume), single track, and very little roads, and don't plan on straying much from home (no overnighting), I would be in the 450-500 range, not bigger. I had a Husky TE510 for a few years. It was about as much fun as you could have with your clothes on, so long as you didn't fill those pants with excrement from twisting the throttle too much at the wrong time (I was a decent rider back in the day, would ride regularly with AMA Amateur qualified guys and have no trouble keeping up).
I honestly regretted adding the power-up kit. It was just too much in the woods (double track and more improved logging roads couldn't even justify that much power). I wanted a little more than stock (around 50hp), but the power up kit pushed it closer to 70hp, and that was just ludicrous).
If it's your first time on the dirt, I would strongly recommend going with a smaller, lighter bike to start (a 250F is a great way to start, and more than enough for most). I'm getting the itch for another bike being in quarantine, and if I was looking for a woods bike, legal to ride to the trail, I'd be looking at a WR250.
After having a wide array of bikes, ATVs, Jet Ski's, Sleds, etc., there are higher performance brands than Yamaha, but I haven't found any as reliable and low maintenance. The Husky was fantastic, don't get me wrong, but it required a lot of upkeep (and as an engineer, I really like working on stuff, but I'd rather ride than wrench).
Even if I was looking at another ADV bike (had a couple, Triumph, Buell, BMW), I think I'd be looking at the Africa Twin over the KTM. I realize I'm not a magazine editor, and don't have those skills or needs. The Honda is good on road, good off road, and reliable as hell... The KTM's are better than they've ever been in terms of reliability, and are hands down the best off road machines out there, but at a cost of reliability and lots of maintenance (though that new 790 intrigues me).
XR650 always struck me as a desert bike. I've ridden one, but just on road. It's a BIG bike (and I'm 6'1). Not something I could see riding single track in the woods, at least not having much fun...
The KTM690 is on like a giant, heavy, dirt bike, though more nimble than the Honda (ridden the 690 Enduro a handful of times). It's an awesome bike, but again, too big for single track, or woods riding. Logging roads, it would be a hoot!
There really aren't many bad bikes out there, and you'll enjoy any of them. Just decide how much you want to wrench, and how much you want to spend on parts, and how good a rider you really are (can you appreciate a WP suspension over a Showa?). Also, it never hurts to learn, and dump, a cheaper bike first, then graduate up to a premium bike.