You could have lost a tire weight, how's the steering wheel? Does it shake?
Less expensive tires probably isn't the issues, it might be improper installation or something missing.
I notice, while driving over 50MPH, the sound from the tires on the road is unusually loud in the cabin of my Acura. Could this be caused by the low quality tires that the dealership installed?
That's highly possible. Usually the softer compound tires are somewhat quieter than the hard compound tires the dealer puts on the car when they're new. When you're ready for tires and usually that first set wears out pretty fast, try Michelin tires. The best out there by far. Quiet and long lasting. Great performance also.