Two or More Subwoofers?

would you prefer to have two REL G-2 subwoofers for you Maggies (or other speakers), or have four R-328's or four R-528's assuming that you would have these set-up in a larger dedicated listening room?
2 G2s - Stereo subs are fabulous for spatiality, and the G series are very fast to blend well with Maggies
I am currently using two REL-328's. Trying to decide if I show buy two more or sale the two and go with two bigger G-2's...
Wow, those are good options! I just recently got into multiple subs after using stereo subs for over 15 years. If you have the room and can keep the quality up, multiples have worked better for me, esp. in a smaller room.
I say it depends. How large is your room? Do you listen alone or with other people, and if so how far appart are they? Or do you move around while you listen?

I believe multiple subs have the advantage of potentially higher SPL (particularly valuable in large rooms), and of smoothing the bass response across various points in the room (see Earl Geddes multiple sub approach).

I run a pair of stereo subs and I'm happy with them. I might consider adding more down the road, but have no burning need now. Bigger fish to catch elsewhere.

I did try the Geddes approach and worked well for me, but stereo subs works better for me now. I listen mostly alone and stay sitting in one place while doing so. If going down the Geddes route, you don't need all subs to be the same. Moreover, your 3rd and 4th sub could easily be smaller and you would loose nothing.
My current room is 17.5w x 26L x 9h. That's 455 sq ft and 4,095 cu ft. I have two REL-328's and Magnepan 20.7's. My amps are the Carver Black Beauty 305's (approx 350 watts into 4 ohm Maggies). Dedicated room is in my basement.

I am getting ready to build a new home (my retirement house) and my new dedicated room will be on the main floor. It will be 18.8w x 29L x 11h. That is 545 sq ft and 5,997 cu ft (or 46% more cu ft)!

With my new room being significantly larger I am a little concered about filling the larger space with bass. The new room will be at a much higher altitude (approx 6,700 ft) than where I live today (approx 700 ft above sea level). Not sure how much of a difference that will make, but the higher altitude should ease the load a bit on the Maggie's panels.
Sounds like you will listen from a fixed position, and I'll assume you mostly listen alone. Hence the Geddes approach probably has rather low value to you.

Then it's a matter of SPL and impact. I would wait until you are in your new room, play around with layout enough, then decide if you need more subwoofer power.

BTW, it might be worth looking into DSP alternatives for the best subwoofer integration and room correction. Something as simple (albeit limited) as the DSSpeaker products (Antimode and such), going all the way to more complex solutions. My only source these days is an optimized computer, so I'm biased towards software solutions, but other options are available.

In my book, with my bias, my 2 cents:
1) get into your new room, optimize layout
2) work on room treatments
3) time-align subwwofer to 20.7 and do room correction maybe only to the subwoofers
4) maybe you need more subwoofer power

I have never heard of altitude affecting speaker performance. I was mile
high way back in grad school and things sound pretty good at RMAF - are
they rocky mountain high on altitude steroids?

. I know it takes a higher temperature to boil water. Is this a planer thing?
Not sure, but a Magnepan has a considerable amount of panel surface area, especially the bass panels which are probably 75% of the total area. Being over 5,000 ft higher in the Denver area I assume that the density of air is lower meaning that it is less work overall for the amps to move the panels; but I'm no physicist!
Thanks Stickman

Envious of your current and future room

I have a 15x27 room and that extra 3 feet would really be ideal.

What area of the foothills are you in?