If you are of "normal" proportions you may do better with a 56cm size. Proper size/fit is most important. Play around with some of the online fit calculators to get a better sense. There is way more to it than just making sure you have top tube clearance.

The online bikesdirect is a reasonable choice if you can assemble and adjust a bike. If not, you are going to spend much of your "savings" at the bike shop paying for their help!