improving bass on large floorstanders....

The benefits of proper positioning and bass traps FAR outweigh any possible benefits of spikes (or cables??). And how can anyone recommend spikes when the OP hasn't even mentioned the floor the speakers are sitting on.

I went to a friends to listen to his system for the 1st time a while ago, and even though his speakers were the model smaller than mine the bass blew me away. I got what he had - GIK corners and 244 walls. Realtraps is another brand, and there are several others.

And how can anyone recommend spikes when the OP hasn't even mentioned the floor the speakers are sitting on.

Nor has he mentioned what speakers he's using. That might help also.

07-24-12: Phasecorrect
what are some affordable bass traps?

Take your original tower speaker boxes, stuff them with wadded up newspaper, and stick them in the corners. That's the most affordable version I know of. I first read that recommendation in a magazine interview with the guys who founded and run Shakti. It's what I use in my HT 7.2 rig with dual-ported Mirage M5si's. Cleaned up the bass quite noticeably.

If you're really interested in hearing clean bass, get hold of any Audyssey equipped pre-pro or AVR. Overall, it may or may not be your cup of tea, but it will almost certainly improve bass performance in a startling way.

Marty