Read Alan's article (and many others) on using more than one sub

My living is on the smallish side - appx 1600 cubic feet - 16'Lx13'Wx7'8"H - it's also on the ground floor of a 2 story garden apt and my wife doesn't like really loud music

So I was thinking of using 2 Hsu Research STF-1's for the subs

Opinions please

Vic, the advantage of two subs, properly positioned, isn't primarily loudness, but greater smoothness of bass propagation.

Two STF-1s, either at midpoints of opposite walls, or in diagonally opposite corners, should be excellent.

JohnK has explained this well but I guess ic an also add on to another article by Alan on the site. If you can achieve 104db with one sub you will only achieve 107db if all things are equal by adding an additional sub. Like John states it helps even the flow of the bass reducing nulls. I for example have a null on one cushion of a love seat, i just dont sit there :-)

What about the 2 STF-1's with 2 pair M2 v3 Bookshelf Speakers and a VP100 v3 Center Channel Speaker?

Sounds like a good setup to me.

Very good, but even better would be a third M2, positioned as a vertical center. Of course, add QS surrounds.

Go with the STF-2 over two STF-1s. One thing you can not get out of two smaller subs is the ability to play the lower frequencies.

I second Rick's suggestion, if you can afford the bigger sub it is worth it to achieve even lower LFE playback. This ability enhances HT the most, IMO.

Go with two subs. The STF-2 isn't much more expensive than the STF-1, so if your budget allows, get two STF-2s,