I have to agree with the people who suggested looking as Surly bikes. I bought a Surly Pacer a few months back and I love it. I'm 270 lbs. and the bike feels very solid under me, but it does not slow me down. The bike is 4130 Chromoly which is used in making bmx bikes, so you know it's sturdy, without being to terribly heavy. It came with a steel fork which I used for a few months before switching to a carbon fork to save a little weight. However, the ride of the original steel fork is so nice, I'm thinking about switching back. Anyway, the Surly is my answer to most of the same issues you had. It's a speedy steel ride that I don't have to be worried about when I want to hammer. I bought it as a frame and fork, so I was able to build it with the components that I wanted and/or had on hand.