Try a nice tube preamp on top... the C28 is just OK, and you can do much better for your money. I've used the Audible Illusions Mod3 and mod3a, as well a a CJ premier 3 and premier 14 all of which sounded great with Mac's...
Do you need/want a phonostage?
You also may want to look into Mapletree Audio. Very afordable and a big bang for your buck. (I'm breaking in the Mapletree ultra 4SE with a MC402... very nice.)
good luck and enjoy.