improving bass on large floorstanders....

I have some 3 way tower speakers that could use some bass improvement...however...if the results are minimal...i probably will any rate...would the addition of floor spikes or possibly a cable change be the answer?...I am looking for tighter, leaner bass if possible...thinking entry DH labs or any rates...what has worked/ not worked for others?
You should absolutely consider spikes, or better yet, outriggers. ( This should really help you achieve what you are looking for.
yes to spikes. Also bass traps in the corners behind the speakers. It will be a very noticeable improvement.
1. More careful positioning of the speakers and/or listener.
2. Attention to room acoustics.
Spikes for sure and it wouldn't hurt to try some different speaker locations. Good Luck.
Agree with all the comments above and add that some cables can help tighten up bass and your suggestion of Nordost is a good one, which worked well for me in the past. Another way is to have a better and more powerful amp.
Getting your speakers situated and leveled with spikes is essential. You can't hear whatever bass your speakers are capable of without them. Getting the speaker positions balanced between optimum soundstage and just-right room boundary bass reinforcement is essential. A high current amplifier certainly helps, as does turning the amp on for awhile to charge up the capacitors fully before playing music. For better bass also consider Transparent or MIT cable, though there are several that do bass well.
Like KR4 says, its the room. Start over with speaker placement. My favorite for proper bass response is the Sumiko master set method. Choose whichever works for you. I never found formulas of any kind to work for me. Good luck.
Tell us more about your system and room. What kind of floors are we talking here? That will be a consideration when considering spikes. If you are looking for tighter bass, you might want to look at your amp. Maybe an amp with a higher damping factor would help.
I'm anti spike having spiked for many years. I use Vibrapods under my floorstanding speakers (Silverline Preludes), although not my sub (REL Q150e) 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.
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.