improving bass on large floorstanders....

I'm anti spike having spiked for many years. I use Vibrapods under my floorstanding speakers (Silverline Preludes), although not my sub (REL Q150e)...it sits on felt pads just to keep it from scratching my floor. I might be nearly alone in this, but it all sounds great in my room with my impeccable taste , amazing ears, and humble demeanor.

Matching speaker bass output to room size and positioning of the speakers within the room boundaries should be your first priorities. Once optimized you can move to room treatments if warranted. Changing cables should be at the bottom of your "to do" list since (IMHO) 90% of the bass quantity and quality will be determined by the other factors.

Tgrisham, did you do the Sumiko Master Set yourself or have someone do it for you?

what are some affordable bass traps?

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.