FWIW, I had a champagne tasting this summer, including a few American sparklers. Moet et Chandon's White Star is virtually indistinguishable (in a blind side by side comparison) with Chandon Brut from California. Note that the Chandon is about 1/2 the price. I give them both about 86-87 points. Good, but not great. Dom is a totally different wine, even though it's the same parent company. My experience with Dom has been the 1990, 1992 and 1995 vintages. I have not had the '96, '99, or 2000 vintages, but I expect that for $130, you could probably do better than the '99 or 2000. It's hard to compare NV Moet and vintage Dom as the styles are quite different. In under $50 Champagnes, some of my favorites are Duval Leroy, Taittinger, Laurent-Perrier, Bollinger (usually a little over $50) and Piper Heidseick. These are widely available. A smaller producer that I enjoy is Jean Laurent (Blanc de Blancs, Rose or Blanc de Noirs--all NV). I will second the recommendation of the 1996 Duval Leroy. It is excellent, and a steal for a vintage Champagne under $50. D-L Femme 1996 is even better, but considerably more expensive, and probably harder to find at this point.
If you are just learning Champagne, try this comparison: Laurent Perrier LP Brut NV(lighter, crisper, chardonnay dominated), vs. Bollinger Brut NV (heavier, yeastier, pinot noir dominated), vs. Piper Heisieck Brut NV (rounder, fruitier, stronger pinot meunier presence). Taste all 3 side by side in 3 glasses, and invite some friends over for the tasting. Not all Champagnes taste the same--but these are all very good!