What would I gain/lose?

Why not get a pair of Opticon 6 mk2?  They're the best speakers dollar for dollar that we have ever heard, and will have a similar sound (but better) than the dual Vokal setup you have going. 

Given how you are using the system, I would also strongly recommend switching that Cambridge unit for a home theater receiver of some sort so you can keep one of your Vokals and use it as a center channel.  Unless you are sitting locked into a sweet spot, watching shows/movies without a center channel is hugely compromised if you are in any way out of the sweet spot.

The idea of a receiver and a LCR system is something I will think about. Trying to stay compact with standmounts that I might eventually move to a smaller office or bedroom.  I have Dali Mentor 6s in my main system and I do like the Dali sound. Thinking of upgrading them to the me Rubikore 6s.  And I am locked into a sweet spot so that really isn’t an issue. 

This is not exactly on topic but, a parallel situation that I had to address and maybe will be of use for someone else reading this. My very elderly mother had a Salamander cabinet with the space for small speakers above the regular shelves. We tried several different "bookshelf" type speakers but, she could not hear TV dialog well enough. Finally, we tried using a pair of center channel speakers instead of regular stereo speakers and that helped very much. Also, via trial and error, I found cables and cords and even a wall receptacle that provided a more mid-range forward sound.

I think you’re missing out on a lot of sound by not using an A/V receiver capable of reproducing multichannel sound to include at least Left, Right, Center and . . . a subwoofer. The difference between a stereo reproduction and multichannel is really quite stark. The quality and flexibility of even entry level A/V receivers is really amazing. My entry level Sony unit allows me to select a stereo-only ‘pure direct’ mode for stereo music listening using the remote, or set up speakers in two additional ‘zones’ which, again are selectable from the remote. Or you could run two systems simultaneously, especially if you purchase an A/V that has a pre-out to your Cambridge. 
I can’t think of a sound issue that can’t be solved with more speakers, said he, facisiously. 

I listened to the Rubikore bookies a few days ago. The 2? Now I really want to hear Epikore 3s. The Rubikore bookshelves were super refined and easy listening with all the details. They're very nice. I think they pair well with Class D like your Evo. I listened on a Bel Canto e1X that sounded fantastic, however note that the Dali sucked up the power. I mean to say, ALL of the power. The Evo75 may not have the juice to completely wake them up.