My opinion is worth exactly shit, but I would take a '04 - '05 ZX10 over the '06 - '07 model anyday. But all those bikes are good for the same thing, some just do it faster than the others. Oh, and for what it's worth, I sold my 2005 GSXR 600 with 6,000 miles for $4,200. So, I hope that CBR is on the low end of your price spectrum and has some nice parts to go with it.