I'm also a firm believer in treating bikes as a "total unit." Let me explain.
I am very dissatisfied with the cheap suspensions Harley puts on their bikes. It's the old game of "over sprung and under dampened." Additionally, the seat on my Sportster was like riding a wet brick. Something had to change.
I did what you are doing now--research. Not only did I change out the seat, but I replaced the rear shocks and ultimately the rear wheel. In like fashion, I also replaced the shocks and front end on my Dyna.
To me it makes sense. If we are going to spend long periods on the road, not only do we want a better seat, but we also do not want to constantly get hit in the tail because of a crappy suspension. The silver lining is that you can buy shocks in any length you want from numerous manufacturers.
All you need is a copper mousetrap and you're good to go...