You really believe all amps sound exactly the same if they have the same power rating?
More to the point, you apparently don't? Even just amps with same "power rating" could mean different capabilities, such as in impedance/voltage rail capabilities. What amps do you find have particularly euphonic sound signatures in your use? Got some examples? Why did you pick those three amps you originally proposed? What's your current amp and what needs upgrading particularly?
My general experience with a variety of amps (have several different ones in use in the house now) is that differences aren't particularly significant, at least among solid state amps as long as they are suited to load/use....some tube amps may have a particular sound baked into them I suppose or just have odd responses to various speaker loads.
It's hard to comprehensively compare amps, too... non level matched and sighted comparisons can be misleading....plus how do you test so many amp choices for a wide variety of speakers or do you try and find some magic amp for one pair of speakers? I certainly wouldn't go by most of the subjective reviewers out there....
My .02
