I've been doing the same thing... going around to different shops, test riding, etc. I would suggest you shell out the $100 or whatever it is and get a professional fit. I actually went to three fitters... paid $100 for one, $50 for another, and the other ended up being free because I just purchased a bike there. Everyone stressed how you need to find a bike that *felt* right but I feared that I didn't really know what *right* meant and that I was going to buy an ill fitted bike. So I got fitted... three times. Excessive? Probably. When all measurements and recommendations came out to about the same, I decided that I had found a match.

Everyone stressed looking at womens specific bike initially but I just ended up purchasing a mens model because it just fit better. I'm not that tall, only about 5'5" but was fit by multiple shops to a 54cm Trek Madone WSD or the 51cm Cannondale Synapse. The Cannondale comes in WSD but the mens model fit better. A little bit of adjustment and I am hoping it'll be perfect. The actual geometry and measurements vary a ton... I thought a 54 was a 54 but that wasn't the case at all.

Gooooood luck!