Yes, the radio tower could interfere with the keyless remote. There is a service bulletin on poor remote reception range though. At your next service, just mention that the car doesn't receive the remote signal unless you're standing right next to the vehicle, and cite poor reception range (leave out the radio tower part)

As for the sound system, there is a tweeter and mid-range in each of the doors, making for 8 speakers. There are two subwoofers located under the front seats. If you wish to upgrade, the easiest way is to just replace the mediocre speakers (4", very shallow depth) and leave the sub as is.