I just followed my own link and they have definitely added a few new wall specimens since I was there last. Need to check in more often, I guess. I found the MLV-wall acoustic tests interesting.
Joel, I do have to disagree with the "MLV adds 26 STC to a wall assembly" statement. If you look at the tests, it clearly contradicts this.
Test OL 05-1003 (5/8" drywall each side, insulation, studs 24" o.c., STC 40) versus test OL 05-0822 (same as above, with MLV added, STC 45) indicates a gain of only 5 points STC. That's a long way from 26!
A piece of MLV, by itself, hanging as a curtain might score 26 (as a 1/2" piece of drywall rates 28) but as part of a composite assembly it's not even close to that and never will be.
Also, a consideration of MLV is price. The cheapest I've found is $1.50/sq.ft, or $48 bucks for a 4'X8' piece. That's equivalent price-wise to 6 regular sheets of drywall. Pretty expensive way to gain 5 STC points!
Green Glue aint cheap either ($30 for a 4'X8' area, in the recommended 'dosage'), but the low frequency isolation it provides makes it worthwhile. Attaining good low frequency damping is most of the battle.
Seatac, you might want to invest in a sound level meter and take some measurements of your noise problem. Multifamily dwellings are required to meet STC 50 between units; I suggest that be the minimum number to shoot for.
But 55-60 would be better....