Greetings,
I am also a 1.6 owner. Love the speakers. They do so many things right. But, bass is weak. I understand that Magnepan does not officially recommend any subwoofer to be used with their speakers, but did suggest that one which will integrate nicely has a configuration utilizing three 8" drivers. The sub that fits that description is the Vandersteen 2 series.
To make the bass on 1.6's really live, bi-amp and bi-wire each speaker. I'm running four channels of 200wpc into my 1.6's. The change in bass dynamics is impressive. But still not enough to satisfy me. So, I went to subs.
I currently use two Vandy subs (older 2W's) with my 1.6's. talk about Heavenly, powerful, defined, etc. etc. BASS!!!
You can find Vandy subs used for about $600 to $700 on Audiogon. GET THEM! They are a treasure for us magnepan owners!
I also highly recommend you purchase two; it's no joke, there is definitely lower level information which you can hear utilizing twin subs. I would not even consider going back to using only one sub. The difference in the "presence" of the music with two subs is amazing.
The only other brand of sub that comes to mind which is to my knowledge geared for true audiophile listening is the REL line. But they cost about three times as much as the Vandersteens.
Visit the Vandersteen website vandersteen.com
to see how their subs take the signal from the amp versus the preamp. A very critical difference, which IMHO is why they are so special.
I am getting UNREAL - NO! REALLY REAL sound from the 1.6 Vandersteen combo! I think you would be impressed!