Others experience re: subs and Magmepan 20

Subs work best with full range speakers, but you have give them the same attention you would give any other part of the system. I'm not saying this is you, but more often than not, someone will put a nice system together, and then buy subs as an after thought. Its a nightmare to integrate a system like that. The sub needs to be in the same league as your other components.

Your situation is a bit more difficult because its always a challenge to integrate a driver with a panel. But it can be done. I'm not too familiar with your current setup, but you need a sub thats meant for music, not HT. I use Vandersteen subs and I have yet to see anything that comes close for the same money. Part of that is due to the first order xover's Vandersteen uses. Not many companies use them in their designs, but if you want the best integration, first order is usually the best way to go. Another option would be to try and find a good used pair of Kinergetics. A lot of people with panel speakers used them.

akg_ca

I was reading through The Chronicles of Narnia and came across this.

"It’s amazing! What’s even better is that the price of the system with the Model 5As and the VT-100 is under half the cost of the Ref 600s alone! Since this discovery, we have achieved the same kind of unbelievable dynamics and seamless blending with ProAc loudspeakers and twin Vandersteen 2Wq 300 watt powered subs. So, if you want the sound of Ref 600s but cannot afford them, buy a pair of Model 5As or your favorite pair of ProAcs plus a couple of 2Wq subwoofers and mate them with a VT100 and you’ll get surprisingly close. You can cut the cost even further by running a pair of Vandersteen 2Wq 300-watt subwoofers with your existing speakers. Or mate a pair of 2Wqs with your favorite ProAc. In any case, it is the magic of SUBWOOFERS that allows this to happen."

If you ever get a chance to hear a pair of Quicksilver V-4's in a system like this, thats based on a VT-100, try them. As much as I liked the VT-100, I felt that the V-4's performed at a higher level.

"My question is less about what equipment and integration issues (that would a whole, complicated discussion alone) but rather other folks experiences who have tried this and do they feel they got substantial benefit from an extra half octave added to (almost) full range speakers to justify the expense, hassle and real estate taken up in the music room."

You can't separate the two. If you put 2 different solutions in your system that both get that extra half octive, they can sound completely different. It's a matter of quality and system matching. Just getting the system to play lower notes won't cut it in your system. I'm not a huge fan of Magnepan, but if there's one thing they do well, its bass. They take the quality over quantity path, and it sounds great. The only downside is that it's harder to integrate a sub.