I would second the ridley recommendation - not many people know more about cross than the belgians.
I would suspect a good cross bike will not ride noticably different than a middle of the road - road bike but will be significantly slower than a high end road bike. I ride/race a wilier alpe d'huez road bike and race a wilier alpe d'huez cross bike (and use it for winter training) and am quite a bit slower on the cross bike. Also, you'll be slower climbing on a cross bike due to the steeper geometry.
I've owned and raced a redline, fort, surly, and wilier. I liked the fort, but it was heavy. I did well on the redline when it made it to the finish, but ended up getting rid of it due to constant mechanical problems. I also bent the fork on it. The wilier is far and away the best cross bike of the four.
As with most bikes, you get what you pay for. The catch 22 of a cross bike is that you don't want to pay too much because it will get trashed, but want to get a nice enough one to last.