I don't use a damper on my Hyper and have never felt the need for one, but I also have had the front end done with RachTech springs. The front end on stock Hypers I've ridden don't feel as stable as mine I must admit.
On the seat i recommend the Sargent seat, although opinions vary and many like the Ducati Performance seat.
Sliders vary all over the place in price, starting with the cheapie T-Rex, which will set you back 35 or so for ach axle and 75 oor so for the frame. I like (and have) the Speedymoto sliders, which were about 60 and 150 respectively.
There's no end in site to what you can do to make your Hyper be better for you. Enjoy your bike.