I'll reinforce the member that always reminds us that a new chain can absolve a multitude of sins. A new cassette would be a great addition as long as the cost are within your budget. If you are shooting for an all Deore drive train they are certainly great components. I am assuming this is for the Trek and not the R500t, and I have been frequently known to use the "assume" to its full split potential.
Which SRAM cassette do you have now, and what condition are its teeth and the pawls for the action still in good shape? If you want an all Deore/SLX drive train, go for it, the chains are some of the best as I understand it. I know of several members that have the Deore drive on touring bikes for the low big cog it can handle as well as the crank and its chain ring offerings. If you do this a ride report and pics are mandatory you know.
Bill
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Semper Fi, USMC, 1975-1977
I Can Do All Things Through Him, Who Gives Me Strength. Philippians 4:13