This is what I use, Oxford lifetime luggage. All in black though.
X40 tail pack. What's cool is that it has straps that wrap around the pillion seat and it expands to 40 litres. Extremely versatile. When you want to take it off you just unzip it from the mount and throw it over your shoulder. No rain cover rather an internal dry bag. On the sissy bar I strap on of my medium size day packs, good for a week of "stuff". I don't waterproof anything, I use internal dry bags you can purchase at any camping store. All I can say is the oxford tail pack is an outstanding piece of kit.
As for a gel seat, have you considered doing it yourself?
http://www.luimoto.com/?p=327
Another great product. The website has an excellent install video.
Cheers