Good thread topic.
You're spoilt for choice at that price point, at least you would be with UK prices, though I'm not sure how expensive Champagne is in the USA. But I'm confident most of the following would be within range, especially considering the case discount you'll get, and the post-Christmas price cuts.
Any of the usual suspect NV bruts would be fine for a party. From the more widely available major houses I'm fonder of Taittinger and Bollinger than some of the others. Piper-Heidsieck is good too.
It really does boils down to the style you like. I prefer a slightly bigger, yeastier/biscuity champagne than the more austere style. That reflects my picks, though Piper is more towards the middle of the spectrum than the other two. Deutz is pretty cool too.
If you want a vintage rather than a NV,
Shaytan's mention of Canard-Duchene would fit your price range, but personally I tend to look for Hiedsieck Monopole Gold Top. Both are nice in their own ways. I find a nice vintage from a house you like is often the better value choice than a NV from the big houses, but for a party, and at short notice, a recognisable NV may be easier and simpler.
If you want something on the more austere side of the spectrum, Jacquesson would do the trick. It's way too low in dosage for my tastes and always manages to give me a slight headache though.