This is really nice discussion going on.
Just adding my 10 cents.
Improving output quality of any audio equipment beyond certain level is really tough job and it really needs lot of investment in R & D and compoenent cost to get that. That's why they charge you 5x (as someone said there is no liner relationship here).
Sometimes it is better investing efforts in finding what works better with what, than just adding up your budget expecting better sound quality.
My personal experience says that some times same setup sounds out of the world to me and some other time I find its shortcomings.
Hence I convince myself that this is just state of my mind at that time and postpone my upgrade plans.