To me the ultimate bass tone is illusive, there are so many great bass tones. "Freewill" from Rush comes to mind. It's almost like all the great bass tones need to be segregated by the make and model of bass they're played on. For instance, In my opinion, the finest Precision Bass tone would be "Budgie" In the Grip of the Tyre Fitter's Hand, give it a listen sometime and you tell me if this isn't the finest P-Bass tone ever. The finest Rickenbacker tone might be Chris Squire's bass work on Roundabout, or the above mentioned Rush "Freewill" or really any of the earlier Rush songs. Great Thunderbird tone would be Wishbone Ash.