I want to get a new bar and chain for my 251C. Thinking of going with a 16" bar but unsure about a chain. Currently have a 26RM 68 on the 18" bar and it seems ok but that chain is no longer available. My dealer has the 26RS for a 16" bar. The only other option seems to be a RM3. I don't use my saw a lot but when I do I want it to cut fast . I would appreciate advice on a bar/chain combo for my saw.