Trying to find the 'perfect' bike is never going to happen. The 650-to-800 is really the right first bike, you won't outgrow it anytime soon but you are unlikely to ever get in a situation where you can't control it as you gain experience.
I really love my KLR. Maybe on long highway stretches I wish it was a little lower & sleeker and had a bit more power, but otherwise I don't feel the urge for more. The only time I want for something smaller is super technical trails but really anything other than a true dirt bike wouldn't be right anyway. It's right at the limit of weight for a day of picking it up, though.
For your use I would think you'd love it. The KLR really handles pretty good on pavement but has the heart of a big dirt bike. Jack of all trades, master of none I guess. Best part: reliable, easy on the budget (actually it's rivals my mountain bike for the cost for two tires) and ubiquitous. There's someone who has figured out everything and anything about them.
I generally get ~200 miles of commuting between fueling stops, which takes about 4 gallons of gas. Not as good as a 250 but the KLR holds it own up to about 70 MPH and usually scares me less in traffic than my 22R-E Toyota to be honest. I've only had it a couple of years but I still smile every time I park it, even going to work or a beer run, just a fun bike all around.
A KLR is something you keep in the stable even if you do get a Dakar or big street bike just 'cause. You'll spend a few grand on a decent one (heck, new our local dealer asks $5,600, which is an incredibly high dollar-fun ratio) and it won't bug you at all that it gets soaked and caked in mud, gets dumped and scratched or to run your booger welds on a frame fix. It's really freeing having a vehicle you
just use. It can be diagnosed and fixed on the trail with the few tools and a photocopy of the wiring diagram you have stuffed away.
Plus, if you bolt liberated 20mm ammo cans on a KTM or BMW you'd be laughed out of the cafe. ;-)