You may be able to get some new old stock LX/XT 8 speed stuff from a shop but I woud question the wisdom or need to upgrade. My rigid mtb has shimano altus derailleurs (the lowest of the named...) and for 7 years all has been fine. It shifts as sweetly as the dura-ace/ultegra stuff I have and keeps going.

As for saddles, I have a brooks swift on the road bike and love it. When I have the money I'll be getting another for the mtb. If you have a wider pelvis than me (which is likely as I'm 5'6" and 125 lb.) then the team professional or B17 may be better. There is a reason you don't get many people complaining about brooks saddles.