Should I use Speaker Spike / Isolation Base or Something?

Noted MC isn't coming in on this.
Boing boing!

Clearthinker is absolutely right. Any vibration of the speaker is distortion. The game is to hold the speaker as rigidly as possible under the circumstances. Springs are beyond belief silly even on a wooden floor which is going to vibrate at it's resonance frequency regardless. A concrete floor is wonderful as least for speakers. Not so much for turntables as there is rumble that will travel through a concrete floor. Speakers should always be spiked if possible. If a stand is used they should be firmly attached to the stand and the stand spiked to the floor. 

clearthinker, you are wrong, wrong, wrong.   Best sound I ever had and I have been doing this over 50 years.   Try some of the GAIA footers and you will eat every one of your words.  Do you like the taste of crow?    And, I will leave it at that.

+1IsoAcoustics Gaia feet

So many posters with the absolute best solution.  If you look, you can find positive reviews for many types of solutions, from both on-line or print publications and from hobbyists on forums such as this.  At the end of the day, you should trust your own ears to achieve the sound you enjoy, which means you should probably try a few different things.
I scanned this thread and did not see whether the floor is carpet over a concrete grade slab or carpet over a suspended wood floor.  Many on this forum have recommended spikes over concrete grade slabs and some sort of decoupling over wood floors. 
If you read the information on the Townshend Audio website, they provide an opinion of why decoupling/springs are a good solution over both types of floor support.  There are several positive reviews (like here and here) of the Townshend Seismic Podium, which is basically a spring-supported platform.  You can try springs without purchasing the expensive Townshend platforms. 
This company provides detailed information such as maximum load capacity, length, and spring rate for a variety of compression springs that you can purchase relatively inexpensively from their website.  You can try simply positioning the springs under your speakers or speaker stands and you can try loosely covering them with heatshrink or placing foam inside of them for damping.  Most try and load the springs to around half of their maximum capacity.  You want enough damping (which the weight of the speaker should provide) so that the natural frequency of the spring/speaker/stand system is below the audible range.  As some have pointed out, Nobsound by Douk Audio offers a product that allows you to adjust the maximum support capacity by adding/removing springs.   
There are other decoupling methods/products ranging from simple hockey pucks (vulcanized rubber) to sorbothane spheres, to products from Herbies Audio Lab products or EVPs by A/V RoomService, Ltd., and more.   
Many recommend spikes such as Sound Anchors, that makes really nice speaker stands.  They send their stands with basic Ramset threaded fasteners, which are used as spikes.  I have used those and have also used really nice large brass spiked feet from edenSound. 
I have ended up with Herbie's Giant Fat Dots in furniture feet protectors on the back side of my speakers and springs in the front....it is a decoupling combination that works for me and my 175-pound speakers on carpet over a concrete grade slab, after trying many.  My two 150-pound subs are completely supported on springs.  When supporting speakers on springs, it is good to recognize that the front side (where the drivers are supported by the baffle) is often heaver than the back end.  You can adjust for this by adding springs where there is more weight.  For example, in addition to springs at the four corners, I have an extra spring directly under the very heavy toroidal transformers in each of my 80-pound monoblock amplifiers, which are then supported over SRA platforms.
Do your own research, try some stuff, and choose what works for you.  Here is an article on vibrations and audio equipment you might look at.  Good luck.