For the long day, long mile rider, my vote is for seat improvement. Nothing will make a trip more miserable than a butt that says "far enough" three hours out of the gate.
The most noticeable modification for the least amount of money and effort is the 22 cent mod, IMHO.
Everything else is just fluff.
ďmany a trip continues long after movement in time and space have ceasedĒ- Steinbeck, [I]"Travels with Charlie"
[FONT="Century Gothic"][I]Sometimes your only available transportation is a leap of faith[/I] [/FONT]