using a sub with full range versus or monitors ?

Your choice-making procedure is, imho, a little backwards. Why decide on having a sub (and a particular one) and then open discussion on the main speakers?

That said, there is an advantage in that (1) using a sub not only increases power handling in the main speakers, it off-loads power demands from the main amps and (2) it allows you to position (and/or EQ) the sub to compensate for room modes while allowing you to position the main speakers for imaging and balance.

Kal (who uses a sub with full range speakers)

I think most floor standers are designed to sound their best alone without subwoofer reinforcement. I just never found the integration to sound as good as a well designed well equipped floor stander, my 2 cents.

There can be benefit with more full range speakers but it depends on the response of the speakers in your room/listening environment and the ability to blend the woofer in a manner that fills in the missing low end without producing excess output at the frequencies the speakers cover. That may require some tricky and hard to achieve crossover parameters. For a more full range speaker, be sure the sub truly can cover the missing very low frequencies down to 15-20 hx or so to start with, otherwise there is no likely benefit save a lot of boomy and poorly defined bass, you know the kind I am talking about, right?

Many smaller and less expensive subs are designed to match better to monitors or other speakers that may only go down to 50-60 hz or so otherwise.

GEtting a smooth blend that truly sounds good can be tricky in any case. That's one reason why educated full range speaker designers make the big bucks! :-)

In general I agree I would start with choosing my full range speakers first and then add a sub later but only one that can be matched well and only if needed, but even then it helps to have the right tools and equipment to measure the results and enable a smooth crossover/blend.

Okay, here's another question. I use Cain & Cain Abby's and a Sophia Baby. I have a NSM 15EXP arriving tomorrow. I will be attempting to make the blend being discussed. Question: run both separate from the speaker taps or use the sub's internal x-over and run amp - sub - speakers?