i've got a pyramid cruiser seat from bikepartsusa.com. it's wide, springy, and super comfortable. Pyramid Cruiser Saddle With Springs Black | BikepartsUSA
knobbys will definitely harsh your ride. my first bike had some old Carlisle Aggressor tires, which are awesome cruiser tires, but like the name says, the tread's aggressive. now i'm riding on Kenda Kommuter's, and it's a night and day difference.
and as i said in my "common sense" thread, solid motor mounts are the way to go.