If you're going to get a rear rack then get a hybridbackpack. I use it to carry my backpack, case of beer or wine. I love it. It allows me to take make backpack.
Check out my Channel on youtube, I have a review of it along with videos of it in use.
http://www.youtube.com/user/bobbisig...r?feature=mhee
The website has many pictures and videos.
Hope this helps