I have an 05 rockhopper and a 02? Diamondback Sorento. The sorento is off the shelf and is starting to fall apart, which is why I got the rockhopper, easier/cheaper than upgrading the old bike, right?
Well, I have started to realize that the diamondback may have crap components, but it has a solid 6061 aluminum frame. Now I want to use the diamondback as my commuter/backup so I figure instead of buying parts for it pull them from the Rockhopper if possible (and if it passes the common sense test).

For the DB besides a new axel for the rear, or whatever (I am a noob forgive me, I think the cartridge is toast on the rear, I have not thought about that yet since it just happened today). The cranks on the DB were crossthreaded by whoever put the bike together and now they need replaced if I want to use it for more than a few miles. I would rather replace the cranks on my RH with something like a RaceFace Evolve DH X-Drive C/Set w/BB ($129 at beyond bikes) and put the truvative on the Diamondback. Is this possible or is there a possible size issue? I am not sure if the Raceface BB will fit in the Rockhopper yet or how hard that will be to do. Is this smart or should I just look for really cheap used parts and fix the DB and save my money for later?

My goal is to make as intelligent and long term, non-impulse buy decision. Sorry about the long post but at least people give honest if often brutal answers in here.