Bit of a Miata fan here (Darling Wife and I have 3.75 between us). As a veteran of multiple topless cross country (San Diego to Connecticut and back) trips, I can't recommend earplugs highly enough. Takes a few minutes to get used to (SO many driving cues are audio when you're in a little 'vert!) but the adjustment comes quickly.

Good plugs will allow you to hear the stereo, hold a conversation, hear sirens, etc - but will kill the din that is so very, very fatiguing.

Funny how different drivers react to the differences between a well-tuned Miata and most other cars - I understand the OP's comments about needing to pay attention - but to me, it translates into KNOWING what the car, and the road, is doing. Softer, more "comfortable" cars make me feel like I'm working harder to pay attention than when I'm driving my Miata - she and I just communicate, there's no "thinking" required.

__________________
1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man - given away
1980 Redhead: Darling Wife