Originally Posted by
roccobike
You can re-use the entire wheel, including the RX100 hub, but to update to 9 speed you'll have to replace the freehub with the 8/9/10 speed freehub referenced by revolator. The RX100 hub will accept the new freehub but you'll have to redish the rim. Still, that's a heckofalot less work than rebuilding with a new hub and it will cost less.
+1
Treefox,
if you can work the redish yourself, and replace the freehub, then thats the way to go.
If your getting someone else to do it, the price of a good used rear wheel might not be much different and less of a hassle. If the frame is aluminum, they advise not to use a rear wheel that doesn't match the spacing.