Tires-
Going from your 2.1" to something like a 1.5" will make a world of difference.
The weight reduction makes accelerating & climbing much easier. Ditto for getting rid of the knobbies.Too much rolling resistance.
Keep in mind that a smaller dia. tire will also gear you down some.

IF you don't need all those low gears, a different cassette may give you more "usable" gears where you really need them.