Rich, you won't go far with the big brands. You want to be looking at something like a Specialized Allez, Giant Defy, Cannondale CAAD 8 and the like. If you're buying new, then most (if not all) will offer a lifetime warranty on the frame and one or two years on parts.
If you see yourself just pottering about and going to the shops and back then I'd maybe consider a hybrid bike but if you see yourself getting into your cycling a bit more seriously and maybe entering the odd sportive and challenge ride then I'd go for a road bike. On a flat handle barred bike you can't adjust your position on those longer rides whereas on a road bike you can shift about from the tops, the brake hoods and the drops.
My top tip would be to go and visit a good bike shop and try test riding any bike you like the look of. Make sure you get sized up properly if you don't know what size you are already.
There are some excellent road tyres out there including some 700 x 25 which have a slightly taller side wall profile which are a bit more compliant than your standard 700 x 23 road tyre. Frame size and geometry are the biggest factors affecting ride comfort not tyre pressure IMO.
