Hi Boogie,
Congratulations on your good taste, I've got a Peloton and love it!
I'm your height and ride a 58cm, with a lot of seat post showing, 56cm would be too small / cramped for me.
Inside leg is only one of a number of important measuements, have they had you on their sizing jig? (a "proper" bike shop would have one. Also worth double checking that they actually mean frame size and not seat tube height - as they're not the same - eg the 60cm frame has a 56cm seat tube).
Many LBS would price match Internet sites for genuine current ranges so it's always worth pushing them for a deal, they'd then be more likely to look after you if you go back for repairs/upgrades.
When looking at "last years" bargains on the internet make sure you check the specs closely as they can change a lot, eg the 2010 Peloton was downgraded significantly from my 2009 version (in order to keep a price point following currency changes).