Granite slab over SubDude?

[jessica.]

I was about to order a SubDude, but I was reading that it may be ok to just take a slab of granite and use that instead? I'm on a 3rd story apartment, I have the Klipsh SUB-10 sitting on the carpet. The purpose is to isolate the base a bit in the room but also to maybe spare the neighbors. It is not critical, but it would be helpful.

Would a 1/2" slab of granite be suitable? What if I just used 4 blocks to put under the legs?

I'll buy the SubDude, but if the granite works then I happen to have easy access to that.