Interesting that you ask this now, as I've been pouring a series of domestic bubblies for our visiting French guests (the rule, of course: no French wines while they're here).
Of the commonly-available-everywhere stuff, I think Roederer Estate is by far the best, though Gruet -- in a very different style -- can be interesting. I guess the Roederer Ros and l'Ermitage are widely-available as well, and I like both in most releases, though I'm not sure about the value of the latter. It
is better than the Brut, though; I fear I'm disagreeing with Scott on this one.
I've never had the much-touted Equinox bubblies, but you'll probably remember the hype. I do know they're expensive.
Among less-available wines, I'm a fan of Argyle's upper-level bottlings.
Here are some notes from a few years ago (the Extended Tirage isn't in there, but all past experiences with it have been very positive).
Local (to me, not you), Westport Rivers can do the occasional good bottle, and probably more reliably fools people into thinking its Champagne than most other domestic sparklers I've served (not to say that people think it's a
great Champagne). Unless you can find something non-current, however, this may not be the vintage to go exploring; they're quite variable.
Thinking about this, I'd probably try to get the better Argyle wines -- an assortment -- and leave the rest.
Kalin makes a sparkling wine? Now that I'd like to try.