Newbie Questions: (1) Do all saddles fit all seat posts? (2) My current seat posts are I believe 31.6 (alloy). I am considering getting a suspension seat post. Couple of questions regarding this. Firstly how do I know that the quality is better than the current non suspension post I have (I want to be upgrading not down grading). Secondly are suspension seat posts any good? If so which ones? How do I know which will fit? Do I need to worry about height and diameter? Cheers.