A little piece of carpet under the HSU would be a good idea. I've read posts on the HSU forum of the subs bouncing around and scratching hardwood floors pretty badly.

2xM80 VP180 2xQS8 2xM3 HSU STF3 LG 60PS11 Denon 3808 ATI 1506 LCR 2xATI 1502 Oppo BDP-83