Why go to 700c? For dirt roads, fat road tires on 26" wheels would be vastly superior in speed, ride quality, handling, braking, and reliability. I think that 700c do cover the pavement A LITTLE more efficiently but you'd have to be a seasoned veteran to notice it. And, if you were a seasoned veteran you would appreciate the advantages of 26" wheels for touring.
Why not consider a REI Novarra Safari, $849? It is a touring specific design, not a mountain bike with slicks. It aleady comes with road tires and a really good looking rear rack. It also has cable actuated disk brakes and the fork has the full compliment of braze ons for a front rack. I imagine it could handle up to 26 x 2.4 tires or as skinny as tires get.
The gearing on the Safari is a 48/36/26 crank and an 11-32 9 speed cassette. It is geared lower than the Dr. Dew because the wheels are smaller. Still, a 48-11 combination on a 26" wheel is a big gear. You would not easily spin out. The gearing of the Trek is way, hopelessly, too big. Your mountain bike probably has a 44/32/22 crank and a 12/34 cassette. A 44-12 combination is much lower than a 48-11 combination.
Neither the Trek or the Kona are touring bikes. They have short chainstays which can cause your heels to rub the rear panniers. You might be able to solve it with a longer rack. But the big thing not in their favor is the wheels. They are both 700c wheels with 32 spokes. Touring bikes with 700c wheels need at least 36 spokes. Touring bikes with 26" wheels can use 32 spokes but the Safari goes the extra mile with 26" wheels with 36 spokes. You could always replace the wheels on the Trek and Kona with handbuilt 36 spoke wheels.
If you just gotta' have 700c wheels, in your price range is the REI Novarra Randonnee. It's got drop bars but you never have to use the drops. It can easily be equipped with auxiliary cyclocross levers so that you can brake from the tops or the hoods. It's got 36 spoke wheels and a 48/36/26 crank with an 11-32 9 speed cassette. It's exactly the same crank and cassette as the Safari but it is geared higher because the wheels are bigger. For this reason it could stand a change of cranks to 44/32/22. A 44-11 combination on 700c wheels is a big gear.
And, you could always change the Randonee to flat bars. The conversion is much cheaper than converting from flat to drop bars. However, you would have to find brake levers that are compatible with cantilver brakes or switch to v-brakes, easy and cheap to do. Neither the Kona or Trek could be switched to drop bars without swapping out their entire brake system. There is no such thing as road levers for the hydraulic brakes found on the Kona. The Trek has cable actuated disks but the are not campatible with road levers. However, Avid does make cable actuated disk brakes that are compatible with road levers.
Disk brakes are nice but they are not a necessity. Cantilevers are plenty strong. In fact, many people deride disc brakes.