I have my PV1 on a granite plinth on top of my carpet (only until I decorate, then it's bye-bye carpet, hello marble tiles, then the sub will just sit on the floor).
I have my sub in the corner of my room that's on the detached wall of my semi, as far from the neighbours as I can get it.
What sub do you have? I think the idea of spikes is to penetrate(!) the carpet to get onto the solid floor beneath. If you don't want holes on your carpet (understandable really), then some form of solid plinth is probably the best bet.
Oh yeah. Ensure your sub is set up correctly too. It shouldn't be booming out sub bass in quiet passages of dialogue, if it is, it's set too 'hot'.
A/V: Sony KDL-V40A12U & BDP-S350, BT Vision, Onkyo TX-SR875, B&W MT-30 7.1, QED audio cables, Russ Andrews power cables.
Hi-Fi: Arcam CD72T & A65+, B&W 602S3, Partington stands, Grado SR125, Kimber I/Cs, QED speaker cables, Russ Andrews power cables.