Currently, I'm running XTR shifters, XT rear derailleur & cassette, LX front and a Sram chain.
If I were buying a new drivetrain, it would be as follows: Shifters and rear derailleur, X.9, front derailleur (doesn't matter, probably another LX, heck Deore works just fine), XT cassette and a Sram chain again.
As long as both are all 9 speed, you won't have any issues.
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