It seems to me the 5200s are the sweet spot in Meridian's line up.

There is no doubt in my mind that your room will need some serious air moving potential if you want to "feel" the sound.

Its my experience and strong opinion that when possible its best to have as much of the full signal coming from each point source. So if one could avoid a sub all together and just get all full source speakers this is best. The result is a more enveloping sound. So I would argue that 5200s are a better choice than 3100s+ sub- for sound and in most spaces.

With the 5200s up front and I am not sure what you will run as surrounds. A thought is to get a sub in the mix for your LFE track. I would think of placing this sub in the best spot at the front of your room so when LFE events occur it seems natural as your eyes are fixed on the screen. This would fill in the little bit of the bottom the 5200s are seemingly lacking. I doubt you would miss this for most music and I find a sub can be distracting for music, but this is simply personal preference.

My experience with the Meridian speakers is they often sound more dynamic and are capable of moving more air than their specs suggest so do not make your decision solely on- well this speaker begins to roll its bass off around 35hz. I bet the real world sound on this speaker is so dynamic that you might think you wouldn't need a sub.

If its a budgetary question, I say get the better speakers (5200) and wait on the sub. Live with the sound and when you add a sub it will add another dimension to it.

best regards,
Jerry

Best regards,
Jerry
Main System: 861v6, DSP8000s in corners, DSP7000s Center and Sides, 1-9 humans.