In general you need about 1/2" or 1" shorter seat tube on 'cross bike. The geometry of the CX bikes is more relaxed and the frames will often be ridden off-road so you need slightly more ma nueverning room.
Regarding the Redline - I've seen them and I was pretty impressed with their Conquest series bikes. I think that they are pretty decent bikes, but I think that Kona Jake the Snake is a better deal than Redline Conquest Pro. It cost about $200 to $300 less and seems to me to be a nicer all around bike. Kona, in my opinion, makes some great bikes, and Jake the Snake became very popular with a reason - it was CX championship winning bike in the USA a few years ago. Some people also like Bianchi Axis, but since I am a much into steel frames, I decidedto build my own Pinarello 'cross machine. It's coming soon.