At least as important as the speaker choice is your choice of amp to accompany the speakers. Maggies really do like a lot more watts, which gets expensive if you like tubed amps. Quads will flourish on moderate power tube amps. As said above, Maggies will sound realistic when cranked a bit, but below that threshold, they sound closed-in and dynamically constrained. I've had my Maggies for 10 years now, and love them to death. Occasionally, I've spent some serious time with Quads as well. They really are exceptional at retreiving low-level detail, and are great for late-night listening sessions where you don't wake up the neighbors.
Horses for courses.
If it were me, I'd also take a really hard look at Roger Sanders's electrostats (his new 10B's). They can really kick butt dynamically, and with the line-drive woofer will give you the gut-punch of solid bass that neither Maggies, nor Quads can deliver. At the same time, they are spectacular at detail and have the "breath of life." Roger wrote the book (literally!) on electrostats. Highly recommended!
Horses for courses.
If it were me, I'd also take a really hard look at Roger Sanders's electrostats (his new 10B's). They can really kick butt dynamically, and with the line-drive woofer will give you the gut-punch of solid bass that neither Maggies, nor Quads can deliver. At the same time, they are spectacular at detail and have the "breath of life." Roger wrote the book (literally!) on electrostats. Highly recommended!