Unfortunately there aren't any 9 speed derailleurs that i know that look really cool.

If the arabesque components are in good shape i would keep them. I'm sure that the derailleur could accommodate an 8 speed if not 9 speed cassette. to my knowledge 7-10 speed cassettes are all the same width, just have different spacing. I imagine your 600 is 6 speed?

You will need to get the frame spaced for a modern wheel (130mm) vs its current (126mm? ) which is very easy to do if you have a good LBS around. I'm not sure if you can use STI 9 speed with that derailleur but you could certainly use the downtube shifters on there (in friction mode if nothing else).

I think it would be cool to get some nice modern wheels, throw on an 8 speed cassette ( 8 speed drive will last longer) take the downtube shifters and turn them into bar ends and keep the bike looking classy.

http://www.rivbike.com/products/show...ts-pair/17-068


that being said... you don't need 9 speeds to handle hilly areas. it is slightly more convenient but you can have good gear ratios with any number of speeds.

Good luck

post pictures