Trek 7.2FX lists for $420
Trek 7100 Hybrid lists for $320
Sirrus Expedition lists for $330
Sirrus Crossroads lists for $330
From what you posted, a hybrid or something similar is what you are after. The geometry is relaxed; that is, you are sitting upright or mostly upright. This is more comfortable than a road bike, especially if you are just getting started.
These bikes come with a triple crank; the gears up front. In the back, the gears have a wide range, usually a 11-32 or 12-34. Combine that with the triple 28-38-48 upfront and you've got gears for big hills and for speeding down the flats.
The stem holding the handlebars is usually adjustable so you can set them just how you like them. The saddles are wider and more cushy; that's fine for riding around the neighborhood but for longer rides you'll probably want something with a bit less padding(the padding allows your sit bones to sink down so far that you end up putting pressure on other, more sensitive areas- not good).
Hybrids have wider tires than road bikes but usually narrower than mountain bike tires. Narrower tires are faster, but not as comfortable. The Crossroads above uses 26" wheels, the Expedition uses the road size 700C(27"). The only real difference here is that you'll sit a little lower on the Crossroads than on the Expedition. The Trek hybrid uses the 700C wheels, the Trek Navigator uses the 26".
Most hybrids come with a front suspension. Many of these are not adjustable which isn't good if you're on the heavy side. The suspension isn't really needed at all on the road or light trails, either. It just adds weight. But they seem to be popular; newbies may feel they need it but really don't.
Same with disc brakes; they are overkill on most bikes. If you are doing a lot of hilly riding in the mud and rain they are nice but otherwise they aren't needed. I have no trouble slowing down/stopping after hitting 45+ mph with my double-pull brakes.
Flat handlebars give you good control at low speed but lack multiple hand positions. After awhile, your hands can hurt. Many people install bar-ends on their bars to give them another hand position. Having the hand turned sideways is more comfortable. Road bars give you lots of hand positions but you are leaning forward more and that can be uncomfortable for some people. It's possible to adjust them higher as long as the steerer post hasn't been cut too short.
My preference is something with the relaxed geometry like the Trek FX but with road handlebars. Trek Pilot, Specialized Sequoia, Giant TCR. They are fast, comfortable and can be fitted with racks for the all important beer runs to the store. Or to work.
Trek, Specialized, Giant, Felt, Fuji, Marin, Cannondale, Kona, Bianchi, Gary Fisher and others will have the bike you are looking for that'll last for years and years. At this point, don't worry about whether one tire is slightly wider than the other or that this gear cassette is a bit different than the other. Just test ride a bunch of bikes, ask questions about proper fit, and have fun.
The most important thing is that you are comfortable riding the bike or else you won't ride it.