I'm the same height and weight, with a 32" inseam. That makes a 57cm a comfortable fit for me. A 56 is doable - I have both sizes - with a longer stem, but a 57 just seems to be a natural fit.

Those Denalis, the first one has a listed weight of 36 pounds and a 33.5" standover. So unless you plan to use it as a resistance workout tool and have an inseam of at least 33 1/2", you might want to look elsewhere. (I suspect that the 36 is a misprint.)

Try your local Craigslist and LBS's.

Shimano-equipped bikes are popular. IMO the price/performance sweet spot in their component lineup is the 105 group.