>I'm afraid you have just identified the one weakness of DX. >There just aren't any really wide, fast primes.
This is very true and a great point. I'll add that, even in FX, part of the reason a zoom lens like the 14-24 can earn a reputation for being better than primes, is because the primes it's competing against just aren't that good.
...and the 14-24 really is that good. I'd certainly recommend this over the 20mm prime, if f/2.8 is really a requirement, but it will cost a bit more.
For my purposes, I don't much feel the Need for Speed in this focal length range.