Harry-
Yes - Trifield seems to produce a slight drop in bass, but I believe it to be more accurate of the 'correct' amount of bass;

Regarding one vs two sw1600s: Frankly you don't need subs at all with the 5200s; I ran music and movies beautifully with 5000s for years without a sub and the 5200s give full range beyond the 5000s.

That said, the sub will add value and strength to the lows, even for music. I say all this to make the point that 2 subs are great for cancelling nodes and providing a bigger listening sweet spot area, but 2 are definitely not a necessity.

If you are budget contrained, consider getting one and trying it out; I believe you will be thrilled with the result; It's all diminishing return - 2 is not necessary; But just a little sweeter....

Regarding the 2 sub connection; I would be predisposed to music setup and go with a main L/R connection; others have rooms with different node conditions and go for front - rear setups; It will depend on your room, your music preferences and your tastes ; there's no single answer; Much of the research says to put them on oppsite walls for node cancellation, with the most optimum being 4 subs, one in the middle of each of the typical 4 wall room; Yes sub level bass is mostly non-directional, but it's still bouncing off surfaces creating some nasty bass nodes at different room positions.

Also keep in mind if you are going multiple surrounds (sides and rears), your limited to 8 DSP channels total (7.2 not a digital option right now with M-)- so 2 digital subs can be a connection issue. If you are 5.2 as most are with 2 subs, no real issues that I'm aware of. That may be another consideration; If you plan on 7.1, you might just stick with the one sub now....

it's never ending.... smile