Upgrading amplifiera.

I can't say I have experience that kind of improvements but I know that good power certainly can clean things up.

I don't think some people understand the importance of good amplification  in the chain and everyone knows the importance of eliminating any weak links in the system.  If I was going to fudge a little on a component it would certainly not be the preamp but rather the power amp, however when you can afford it you will want to upgrade this amp as funds become available.

Anyway most upgrades that are done to amplifiers recommended by the manufacturer do make a significant improvement. However I know some people that have spent money on upgrades only to realize that the magic that was originally there was upgraded out and were disappointed in the end but this may be a rare occurrence.

All that really matters is how well the amps work with the speakers you are using.  If you're upgrading to improve some performance aspect (for example, need more power on a difficult speaker), that makes sense.  But most times it appears that people are bored and are changing for something new, but that's not limited to amplifiers.