Clydesdales/Athenas (200+ lb / 91+ kg) - Do I need a larger frame?

I have put ~1k miles on my K2 roadbike, and really enjoy it.. but it seems like maybe I should have a bigger bike. I am ~6'2", and my bike was a "large" (which I think K2 defined as for people 5.6 to 6" ish? 55-57 cm). Because of the layout its probably not accurate to give a CM from bottom bracket to where the seat post is..

Pic: http://flickr.com/photos/sirstan/2425976462/sizes/l/

It has 175cm crank arms, and it seems ok... would I benefit in anyway from a larger bike?

I am 6'3" with a 33" inseam and ride a 61 cm Jamis. Each brand is a little different. I can't tell you, but your LBS should be able to do that for you.

I am 6'3" with a 33" inseam and ride a 61 cm Jamis. Each brand is a little different. I can't tell you, but your LBS should be able to do that for you.

I think you BOTH need bigger frames....
I'm 6'4", with a 34 inseam (pants, not my "cycling" inseam), and I rode 62s for years because that's what most shops carry ("We'll put on a longer seat post for you"). When I bought my Atlantis, Rivendell's sizing chart put me on a 65, and I bought a 64 because they didn't have the larger frame in stock. It made an immediate, dramatic difference in my comfort level.
Only the rider can tell if he's comfortable on a bike, but if I were shopping, I'd at least try one size bigger than the shop recommends. If you look at people you see riding by, a lot of them are on bikes that are too small. They'll have eight inches of seat post sticking up, and they'll either be reaching down to the bars or be riding with a stack of spacer.
An old-fashioned rule still works pretty well: When the bike is set up the way you want it, close your fist around the exposed seat post. If your hand doesn't cover it, the frame is too small. By that standard, 90 percent of the riders you see these days are too big for their bikes.

Bike sounds small for you, but it depends on your proportions, not just height. I bought my 54 cm used from a guy that was 6' 1", but he had a short inseam. I am 5' 11", and short inseamed as well. A lot of people my height are riding larger bikes..

I don't have more than a handful of seat post exposed (2 to 3 inches or less).

I am 5'10, but I have a 34" inseam with bare feet. I went looking to buy a bike last month, and every store I went to wanted to put me on a 56cm bike. I told them that was too small, I wanted to try a 58 and 60. I had one girl actually laugh and say that would be WAY too big for me. Needless to say, I didn't buy from her. In the end I got a 60 cause it felt less cramped (I have 5" of seat post exposed).

Every bike is different though, so the only way to know if you'd benefit from a bigger bike would be to try one. I found a link in this forum (sorry, I don't have it now - can anybody help?) to a site that has a fitting calculator. You plug in all your measurements and it gives you the dimensions of a bike to fit you. I plugged in mine and got the exact dimensions of the bike I bought.

I'm a shade over 6' and am much more comfortable on larger frames. My MTB is a 22", my old Schwinn commuter road bike is a 62cm and my new Schwinn road bike is an XL.