Upgrading amplifiera.

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.

Why do some people who have for example a 100 watt amp, upgrade to a 200 watt amp, same make. Do they think that another 100 watts would make for a significantly better sound. The only reason I can think of for doing that is that you love your amp, bought a set of hard to drive speakers, and want to drive. 

I mean what the heck. There has to be a better sounding amp out there. 

i upgraded from the 200 wpc Ayre VX-R to the twenty series, significant change in circuit typology, operating temp, warnup time to sound optimal ( always on to 15 minutes !) and in sonics

not saying every manufacturer upgrade is this significant or pricey but IMO worth it.

i seem to have gravitated to and value gear from company that offer upgrades - ARC, Ayre, Aesthetix and Vandersteen.

i have so far upgraded the Aesthetix and Ayre, the others so far have no offerable upgrades...

Without picking on anyone in particular, there are some wayward responses above. The correct answer is that it all depends. The amp has to mate with the loudspeaker. A 16 ohm ultra sensitive horn doesn't need much more than a watt or three and a planar may need a utility sub-station. Pass Labs covers the gamut more than any other top manufacturer in that regard. Beyond a doubt, some enthusiasts become fixated on amps as the focal point of their system just as others focus on their ever-changing search for the "perfect" loudspeaker, etc. Personally, if a speaker is hard to drive and has contorted impedance curves and phase shifts, I wonder why bother. The analogy is to the old perhaps outdated scenario with MS vs. Apple-MS operating systems were designed with the idea that if you threw enough computing speed at them they would work fine and Apple operating systems were designed to be less taxing. Unlike the three major OS's (Linux, Apple, and MS), there nearly unlimited choices as to loudspeakers.