you WILL need longer forks, otherwise you bike will ride horribly!! Theres a fair few forks that you could use though, dmr, charge, surly, identiti....they all make longer forks with disk mounts....they are heavy though, but still a LOAD lighter than your sus forks. Also, the front rim sounds fine, most rider run wider rims up front than 25mm, but rynos are pretty good rims, if you really wanted to shave weight try drilling holes between the spokes. Ditch the tyre though, choose what you want tyre wise, but maxxis single ply, kenda stick-e and try-all front tyres are popular.