Sonus Faber Venere 2.5 amplifier Recommendation

I don't know if it will better the sound or not by de-coupling from the concrete. But it will change the sound. I would buy the 6" ceramic tiles and buy some kind of foam or cut some thick carpet to put between the tile and the concrete. Just experiment and you'll find something that works. Good luck.
Dont give up on those speakers. They are very good and will respond to up front changes very well. They have a little bass hump at around 80hz, but it helps with rock. 

I also had the 2.5s on a concrete slab in a good-sized room and couldn't get rid of bass hump.  This bass issue has been noted by some good reviewers, and you can see it clearly in the Stereophile performance measurements...
https://www.stereophile.com/content/sonus-faber-venere-25-loudspeaker-measurements

The only ways I could think of to deal with this effectively, short of adding a sub (which is not a bad idea BTW), would again be to try bass traps or possibly some form of equalization.  Best of luck. 

I had a pair of Sf 3.0 and liked very much the way my Mcintosh MC 152 drove them (with C50 pre amp). Any decent to good amp should be able to get the job done with ease as I did not find them hard to drive.

Depending on your budget, at $2K a Conrad Johnson MF2275 should give you what you want.

Ended up with a rogue chronus magnum ii. Breaking in now .but so far so good