Efficency- Low vs. Hi?

Its all about synergy except with the most non linear loads. There are some speakers that just won't be satisfying without power. Apogees come to mind, you can read a million threads on how they really need a fairly powerful high current amps because of their impedance drops. On the other hand I have a fairly low power 40 watt Consonance tube amp driving 88db 6 ohm speakers (VR2s) as long as you don't ask it to blow your head back they have very pretty sound and stage well. In addition I have rock the house as loud as you can take it sound from a big efficient horns with much less refinement, but still pleasing synergy with a 50 watt Mac solid state. If you really want full sound from your system you have to dump the Cambridge or your speakers they are clearly mismatched for that purpose.

You should be less prone to audible grunge from some of the low level electrical noise sources, and this can save bucks on noise reducing / isolating gadgets and whatzits.
Also if you go tubes all those big glowing bulbs look cool.
Else, besides what was said previously about getting good bass from a smaller box, I don't know of an upside.

I'm not familiar with the PSB line but don't they have some floor standing models that are more efficient? If you keep your amp but change speakers, won't you get a lot more "bang for the buck"? I just looked on ebay and saw a pair of PSB Alpha T speakers with a "buy it now" price of $298. Efficiency is listed as 91 dB which means they should play as loud with your amp as your Minis would play on 200 watts/channel. What about those Status Golds that everyone raved about?

The stratus series IME is hard to drive in general and has to be pushed a bit to open up. I was able to drive a pair of stratus silvers with a 60W rotel amp. This was a seperate amp that weighed 20+lbs though. The silvers didn't really shine until I got a Bryston 3b-st.

Amps are a good buy used. If you can use the Cambrdige as a pre I would pick up a 100W rotel amp from as few years ago and try it out. You can add a real pre later if you want. If that doesn't help then the Mini's aren't for you and just move on.

There are so many medium and high efficiency speakers with excellent sound that I see little reason to use low efficiency speakers. Only exception to this statement is if you gotta have something like a big Soundlab electrostat or Acoustat vintage electrostats.