I have a 2007 Redine 925. It's a 56 cm and I am 6' tall. I ride it but could have used a 58cm. I need a lot of stem and seat post.
That being said there is some info out there about the sizing being changed from 07 to 08 and a 07 58cm will fit more like a 08 54cm. Google it.

http://www.google.com/search?client=...UTF-8&oe=UTF-8

My answer to your question is the 54cm will fit you better than a 56cm

Check this PDF file.

http://www.redlinebicycles.com/adult...08_RL_SPEC.pdf

I like the bike a lot, it's great on longer rides but I have moved on to more aggressive geometry. Have fun.

My 925 http://s41.photobucket.com/albums/e300/tmh657/Redline/