New efficient speakers - best way to keep noise floor down?

What is the rest of your system. The way the noise floor gets reduced is equipment with equipment that has low internal noise levels. A quiet phono stage is a good start, but you also want a preamp and amp with low noise levels.

Agree with Chakster. There are too many variables. I have Devore O93's and tube gear every step of the way to the loudspeakers and I used to have a hum problem with my VPI table due to a grounding issue. My other deck, a hot-rodded TD124 with a Reed 3P had zero hum. I believe my hum problem had to do with VPI's inferior and sometimes problematic grounding scheme with their junction box. Reed (and several other great arm designs) incorporates a cartridge clips to RCA continuous wire (no breaks along the way). My belief is that this reduces the chances of hum greatly. Shielded IC's from the phono stage to the preamp and from the preamp to the amp also help. In my case, I run balanced-Cardas Clear Beyond-from my preamp to amp. So I got rid of my VPI Prime and replaced it with a hot-rodded Garrard 301 with another Reed 3P and though both decks sport low output MC cartridges, my system is dead quiet on most days. Sometimes when the power lines are noisy, I hear very slight hissing. 

What may affect noise floor? The gain of the preamp and amp with regard to sensitivity of the speakers. It can reveal noise in the upstream components. May not be a problem with the right cartridge choice.

And of course, the amount of noise on the AC line coming into your house. Has this ever been noticeable before, and do you use any power conditioning?

good point, I do have a passive preamp (well in tube mode it has 1DB gain). My phono preamp does have adjustable gain settings. Right now I'm on the 48db setting, I suppose with the new speakers being efficient I could lower that to the 42db setting or even the 32 db setting (has the best SNR of all 4 settings). Keep forgetting my phono has those adjustable gain settings... This makes me feel better :)

The status quo for tonearm to phono stage cable’s is horribly flawed. You can help keep the signal free of interference by changing from “shielded” cables that use one of the signal-bearing conductors as “shield” to shielded twisted pair cable and XLR connectors. The shield on this cable is connected to the tonearm ground, and is grounded at your phono stage. This is your best opportunity for rejecting  induced noise on a vinyl playing system.