Impact of speaker stands?

The drivers in the JBLs will be contributing something to the mix just from the fact that active speakers are on top of them...so there's that...also I've found that small-ish conventionally stand mounted speakers have a "singing" pleasant quality if there is less stuff to couple with around them. There is some discussion regarding "spikes vs. rubber feet" where the rubber might be winning in many cases...I put Vibrapods under my skinny Silverline Preludes and they sound better than they did with spikes...go figure. Some high end speakers are being sold with some sort of "decoupling" feet these days...fanatical indeed.

Factors to consider are height ability to tilt if needed and if stands couple to floor or isolate.

I have dynaudio stands that couple to floor that work best on a more solid foundation and isoacoustics brand stands that sit lower to reinforce bass and also decouple from the floor which helps keep bass clean on less rigid suspended plywood floors on upper levels. They also provide option to tilt up which helps with lower placement.

I also put my ohm 100s on auralex sub dude platforms to isolate those from unwanted floor interaction on the same upper level. Not needed in finished basement where floor is thin dense carpet and pad over concrete foundation.

Stands are a must, as your set up now does not isolate the speakers and no matter what padding you use, it will be truly isolate them. Best to find stands that you can spike on where they meet the floor and also spike them where the speakers meet the stands. Yes, it is called a 'double spike'. Don't use blu tack or moon gel. Enjoy.

There are many articles on the internet about the speakers stands (use Google). There is also the litrerature dealing with this subject, for example Jim Smith: Get Better Sound. However, the stands must be rigid and must damp the vibrations as much as possible. Considering the height of the stands, there is "golden rule" - the tweeters should be as high as the the listener ears. I think, the placement of your Kefs on stands would be better solution.

Set Symposium shelves between the speakers. Tweeters at ear level and short out the unused speakers with some speaker wire (plus to minus) or get stands and put Symposium shelves underneath or on top of the speakers and put the other speakers in another room if you are not using them.