I own the Contour 3.0's, and the local shop that carries Dynaudio is first rate all the way, while the shop that carries Revel has them set up in a display room that has all sorts of other gear in it and a 2-story glass wall along one of the long sides of the room, so I have no real hands-on experience with the Revels. I have found the Dyanaudios not only positively enjoyable, but anything other than laid back. In fact, given that the Dynaudios have first-order cross-overs and the Revels a higher-order crossover, I'd expect the Dynaudio to sound more up front. In any case, I find the Contour series to be very involving.
The Revels have been so well reviewed everywhere, both by professional reviewers and by owners, that it's hard to imagine going wrong either way. It is true that for some strange reason, you can find the C5's very cheap slightly used much easier than most other Dynaudio models. In any case, my advice is that you should step back from the price and ask yourself if you have a clear favorite regardless of price, and if the answer is yes, find a way to go for it. The LAST thing you want is to be sitting there listening to the C5's (hopefully for years and years) constantly thinking, "man, I wish the price on those Revels had been a little better!".