Brian's point on 'looking to the intended function of the seat' is spot on. A racing seat is not going to focus on comfort. The original seat is perfect for me and I like how well the designer has come up with a seat that fits the philosophy and design of the car. With the intention of saving weight and making it pretty thin and light, it is easy to understand that any additional created rigidity of the car is going to really make noticeable how thin the seat really is.
On a lighter note, you could try squeezing in a comfy old, favourite lounge chair ..
But, seriously, the best bet would be to take your original seats to an upholsterer (or auto trimmer, or whatever you call them in the States), explain what you are trying to achieve, and let the expert match your original seat, your aspirations (and shape), and the other design constraints within your vehicle so as to produce something a little more comfy yet without creating any other modification issues.
Bonus is that it would still 'look factory' .. and you could even explore a leather colour change to something you prefer while you're at it (assuming you are starting with a leather seat, that is).