Sizing

[B1105]

I'm looking to get a Redline Conquest used. Its a 53cm c-c and 53cm tt. My question is, is this the right size? I'm 5'9" with a 30" inseam. My current road bike is a 55cm c-t and feels good. The selller claims that he also has a 30" inseam. Is there any leeway for sizing in cross bikes? I would like something thats relativley easy to dismount and definitley don't want something too big.

Thanks

Byron