Magnepan 1.7 to 3.7i or Pass Labs XA60.5 to X100.5

Keep the 1.7s, keep your amplification. If you really want to energize the room, improve tonal balance, and have a rig that sounds right on any kind of music, spend your money on one or two (preferably sealed) subwoofers.

JL Audio now has the more affordable Dominion and e-Sub lines. e-Sub also has a high-pass network which could reduce strain and increase dynamics in the 1.7s. They have been enthusiastically reviewed by TAS. I have a pair of Mirage MM-8s which are pretty similar in performance to the JL Dominion d108s. I can't *believe* what good sound I get out of my rig. It really popped into focus when I got the phase control dialed in right.

Anything from solo instrument or voice up through acoustic ensemble to classic rock to brash big band to full scale orchestra and chorus or opera, it just plain delivers, and the subs take care of the bottom octave while letting the 1.7s shine from 45 Hz on up.

I recommended the subs because I have successfully done it. The DOGMA against integrating subs with Maggies is that the Maggies' rise time (i.e., speed) is too far ahead of subs you'd put with it. That may have been true ten years ago, but there are many fast self-powered subs today.

I have two very small (9" cube) Mirage MM8 subwoofers in stereo. They aren't the deepest, but I've had little trouble integrating them with the panels and adding nearly an octave of bass extension and in-room power response.

They really popped into focus when I used a mono source and tuned the subs' phase controls (a continuous 0-to-360 deg. knob), one subwoofer at a time, until the bass snapped into focus.

The other approach as Lostbears mentioned is the Magnepan bass panels. They are so fast their frequency response can extend up to 7 Khz, so there's no problem matching speed and rise time in the 40-80Hz region. If you have the room and placement options, they're a perfect augmentation to the 1.7s. You get a piece (or two) of the 20.7 bass panel but a lot more placement options and a lot less cost than upgrading to 3.7i's.

Finally, I agree with Zd542 that the 1.7's bass quality is excellent. However, unless there's a fluke in the room acoustics or a miracle in speaker placement, you may--as I did--ultimately find the overall tonal balance a bit thin and wish for more bass quantity. One or two DWM panels or small sealed subs (such as JL Audio's Dominion d108) will do the trick.

You still won't get subterranean bass, but you'll get good sub integration and a very engaging tonal balance. You'll no longer have to listen around the 1.7's quick rolloff that starts around 55 Hz.

09-14-15: Russ69
No brainer, 3.7. They are a big step up from a 1.7.

It's a 10x12 room. Think small, the size of a fourth bedroom or "bonus room".

A .7 would probably be better than the 1.7 in a room that size. All the more reason for very small subs to fill in the bottom. Even one DWM may require too much space around it.

Hasse: Thanks for the updated dimensions. I'd either missed or forgotten them. 15x18 is a pretty ideal size for 1.7s and possibly a bit of a squeeze for 3.7s.

Advantage of the 3.7: true ribbon tweeter section vs.1.7's quasi ribbon. You get faster more detailed treble and more bass with the 3.7i's, which shouldn't be surprising for three times the price. I'm pretty sure, however, that the 3.7s need more free space around them to "sing."

On another note, although the Pass's specs say 60/120 wpc into 8/4 ohms, Stereophile's measurements of the XA60.5 indicate that it's putting out 200 watts into 4 ohms by the time it reaches 0.1% THD.

Given that I have an old Perreaux PMF1150B making 100/200 wpc into 8/4 ohms to power 1.7s in an open living space, your Passes should give either 1.7s or 3.7s plenty of power to reach lifelike levels in your 15x18 room.