I've been riding a Kettler Silverstar with a step-through frame year-round in the DC/Northern Virginia area for over eight years. I put in equal milage on my car and bike, and the bike is more reliable than the car, in terms of scheduled and unschedualed maintenance as well as down time. I treat the bike like a car - hop on and go, take it to the shop for all repair work, fiddle with it only in an emergency.
To get this reliability, you will need to fit Marathon Plus tires with Mr. Tuffies inside.
The area is fairly hilly. I think you will need at least seven speeds. Then again, I frequently haul a trailer with over 100 pounds of groceries or a child on a Trail-A-Bike, so I may have more need of gears than you.
Get a bike with a hub dynamo. Sidewall generators require fiddling and will drive you nuts.
DC has a freeze and thaw cycle in the winter, so studded tires are a good idea. I use Nokian 106.
Drum or disk brakes are much less trouble than rim brakes.
After eight years, the rear fender is rusting out. The bike is aluminum, but the fender is steel. Can't say I care for steel. The saddle wore out after a few years, so I replaced it with a Brooks B67. That one is showing no signs of wear. Otherwise, the bike has held up well for over 20,000 miles.
Full chaincases are hard to find. Still, fenders and a partial chainguard result in over 5,000 miles per chain. That's not terrible for a chain that rarely gets any attention.
Kettler is the second-best German bike. Utopia is the best, but they are way over your price range and you would have to import it yourself. In terms of transportation utility, though, the bikes are equal.
In summary, my Kettler has the utility of the Dutch bikes but is much better suited to hilly terrain. I find it the ideal vehicle for this area.
Paul