Going to add a link to some info about the silent JT front sprocket - maybe it will help others http://foc-u.co.uk/index.php?topic=23903.msg297326#msg297326
Worth buying, as they are only around a pound more expensive than standard code is JTF513RB
If you do go the DID chain route buy from a reputable source as there are fakes cropping up and are difficult to tell apart until they break of are worn out in 2000 mile.
I have used AFAM, DID, Regina and Izumi chains over the last 40odd years without any issues. I have also used JT sprockets, Ognibene sprockets and AFAM sprockets without issues.
Generally I change the front sprocket every 8 to 10000miles and chains and rear sprockets last around the 40000 mile mark, but then I also have a Scotoiler fitted which helps.
I presently have a DID HD O Ring on the 1000 which has 23000 miles on it and replaced the front sprocket at the 10 and 20000 mile mark
Last chain I fitted to the 600 was Yamaha OEM as I got a NOS kit for £120.