My Rel's amp went to Sumiko for repair; should be in my hands yet this week. I'm changing room placement and will try the granite slab again. Read the reviews of the Sub Dude and it sounds like it might be perfect for apartments and condos. If so, I'd be afraid it might muffle the bass.
What's under your sub?
Some sub manufacturers recommend placing a down-firing sub on a slab of marble/granite when the listening room is carpeted. Has anyone had any luck with that? I tried using a granite slab under my REL Storm III and found that the bass was much cleaner with the sub on the carpet and not on the granite. I have carpet over a concrete slab. Don't know if that made a difference.