Should I use Speaker Spike / Isolation Base or Something?

Depends. Lots of unknown variables.  You can't go too wrong with spikes through the carpet into the wood floor. Paving slab on the carpet works too, especially with your plastic feet.

I've tried a lot of spikes, Cones, different materials. Best by far are Townshend springs. But if you're on a budget you can DIY springs from eBay, or use Nobsound springs from Amazon. Incredibly cheap, they outperform a lot of much more expensive solutions. Also they are adjustable for weight. So if you decide to upgrade to Townshend like I did its easy to move the springs to use under other stuff like turntable, CDP, amp, etc. See threads around here for more info.

The route is not conclusive as I thought. Kind of tricky situation indeed. 
Thank you for the advice. 

Let’s start with: how heavy are your speakers?

Heavy? Perhaps wheels!  Of course spikes make sense theoretically, but why sacrifice flexibility (alternate toe-in, alternate locations) for theory if you don't benefit from the theory.

I've always had heavy speakers. I've done spikes, feet with textured grips for carpet, thin felt disks to not scratch wood floors, and wheels (3 not 4, more weight per wheel) (rear corner blocks slightly shorter than the rear center wheel, to prevent tipping).

Nothing is lost when going from spikes to wheels if heavy enough. i.e. 80lbs? go to home depot, pick up an 80 lb bag of cement, it can be on wheels and not vibrate. I'm not sure what the minimum weight is when spikes might be advantageous. I would buy some spikes and compare them to the factory solution, simply listen. 

I believe in having ease of movement (mark your best positions somehow), I adjust toe-in when others listen with me to get a wider center, each of us hear both channels well. I push them half way back or fully back depending on size of dinner party, big picnic/crowd, all entension leaves in the dining table ...

btw, it's weight per contact area, with spikes, the contact area is the area of it's protective disc, and that is about as big as a small felt or plastic self adhesive button. something small in the 4 corners, or 3 wheels for very heavy speakers is my recommendation.