Those two are extremely subjective. Travex is right, start with the seat leveling; good place to start. I didn't notice a big difference, but it didn't make it worse. My candy ass can't take real long rides. I had an ST1300 that had a gel OE styled seat. The gel made a huge difference. There are plenty of guys here that have changed out their seat, and can provide better opinions/advise.. . . . Wondering about the other options, Sargent, adcox, etc.
Still trying to decide on panniers too.