what are you plannig to ride?
urban = hardtail
trials = hardtail, fork suspension optional, seat optional
XC = FS or HT
Freeride = FS or HT
downhill = FS (HT is not the best idea)
it depends a lot on what your riding. i do trials/urban/XC/freeride, and a Hradtail works great for me. u say u have a bad knee, so to limit the abuse on it, depending on your style, FS isnt a bad idea. it does mean the bike will weigh a bit more, but thats ok right?
i only ever buy Norco's. it may not be the best idea to limit what i ride, but they offer something for everyone, so its not so bad.
www.norco.com the 2008 Norco's come out Aug. 30, so ya. a good idea is to get a 2007 model on sale this winter (if u dont mind the wait). that way you can get a bike worth $800 for $650.
anymore questions just ask me. ill answer messages faster, so ya.