Originally Posted by FatBomber

I once made the mistake of buying a bike too small for me because it was a deal.

DON'T DO IT!!!

My experience - 6'3" on a large Jekyll when it should have been an XL because it was a "deal":
You will have to use long stems and setback seatposts to make it fit and those items will make the bike perform poorly as you will artificially alter the geometry. The long stem will make it steer slow and will put weight further at times, making the bike want to front wheelie. The setback post will place the majority of your weight further back than designed for and will make your front wheel super-light on climbs in the saddle with a tendancy to pop up and stop you dead in your tracks.

You'll have a less than optimal experience and will eventually buy the right bike.

OR

You buy the right one the first time.