Billybob, I can understand how one could arrive at this conclusion given my stated belief that "high end electronics are virtually indistinguishable from well designed budget or mid range electronics". Let me ask then, are you suggesting that you believe it doesn't make sense to think of budgeting electronics as a percentage of overall budget past a certain point, or are you just being rhetorical?
If you're being rhetorical, I'd respond by saying that people who are prepared to spend several thousand (or tens of thousands) on sound equipment probably don't have a budget at all, so thinking about budget allocation loses its relevance. The goal of my post wasn't to renew a debate about whether there are sonic differences between high-high end electronics and mid-high end electronics, although I suppose I lit the fuse on that one in my original post.
If you're making the point for reasons beyond rhetorical, I appreciate your drawing attention to the outer limit of this sort of budget analysis. I asked the question because like many people, I build my systems (both headphone and speaker) a little bit at time, making upgrades when I can afford them, and I often wonder would would be the most cost effective upgrade.
Bigshot said it - I wasn't being rhetorical in my statement that past a certain point, spending more on the electronics doesn't really make sense, and therefore the percentage formula also doesn't make sense. I guess I approach this problem in a completely different way - I select the headphones I want to buy, then I think about whether an amp is really necessary for those headphones and if it is, what amp should go with those headphones. What gain do I need, do I need a portable, do I need a dac, etc. At my low-budget level, I would rather just have a reasonable amp that can drive the types of headphones I'm likely to buy, then from that point forward, I can swap headphones as my budget and interest allows. If I buy another amp, it's because my old one stopped working (eg, when I fried my little Xenos) or because I simply wanted to add it to my stable. (eg a used AMB mini^3 that I really didn't need but was a good price). For sound differences, I look for headphones, not amps. You'll note that I'm not talking about tube amps - that's a different game...