@han,
i am not sure i understand the point you are making!
the mathematics i made regarding rail voltages for a certain power rating is based on sine wave analysis, another way of looking at audio amps is that they are also dc voltage to ac voltage converters!
they operate on a certein fixed rails and convert this dc rail into ac output in response to an ac signal input!
the output voltage to input voltage ratio is what we call voltage gain, Av, or simply gain. hi-fi amps and pro-amps are not exactly the same! as both are designed different with operating conditions in mind.
hifi amps can have a gain of 20, whereas the pro amps can have gains as high as 40.
then there is frequency response, or power bandwith! hifi amps need to have at least 20hz to 20khz , while the same is desired for pro amps, as many are capable, pro amps are sough for their power delivery as they are often used in sound reforcement venues!
these things i post here did not come from me! i learned them in the course of my being an audio diy hobbyist!
theory and practice are inextricably inter-twined you can not have one with out the other, at least this makes sense to me.
and it may interest you to know that i am not a subjectivist, but i am open minded enough to distinguish audio facts from fiction! 
2ny
its good to know youve learned a lot from your hobby, i too learned from this hobby until i made it a career, but i learned a lot from my father which was a retired sound engineer, he worked for Manila Garden Hotel and Holiday inn. He also participated last "WOODSTOCK 89" as a Audio Director which was held at Amoranto Stadium and Antipolo. so from childhood and then on, ive learned a lot from audio technology. my first Audio gig speakers was the JBL's Voice of Theater which has a bi radial horn and polyplas full range horn driver and my power amps was just a mere harman kardon pro's.
as per expirience, I too has accidentially blown speakers and literally see my power amp in flames! as i load it with a folded horn on a 2ohm/1500 watts load and it happen in public (landmark food court), i was so ashamed i have to use a fire extiguisher.
My point of view is some of us has enough expirience to give advice to our fellow audiophile enthusiast, so they will prevent such mistakes as we did. dont just rely on numbers indicated on your products specification, there just there to give you the right guide. that is why i kept on giving the quote "trust your ears!" some speakers would give specification as 15hz to 30khz rating. low freq below 20hz in the right tune will literally move things, you will no longer hear it, but feel it. thus also giving unwanted noise and beyond 20khz will put you into ultra sonic waves which is being used destroy to drive away pests and insects hehehe!, see my point? anyways human hearing perception is only 20hz-20khz.
so your point about DC to AC conversion of power is not the only thing, you should also note amplification and electronic impulses, thats is why some amps poses direct link (e.g. tube amps), that means the sinewave are going direct to the amlplification area to again convert it into higher voltage gain such as you said. so pure signal are being sent, no coloration or proccessing just pure amplification. but in the case of digital signal such as fiber optics etc. some amps will convert analog to digital thus giving almost 100% signal, i agree with you about the difference between hi-fi and pro-audio they both depend on the end user.
good thing for now i just made audio as a hobby again, because of this Home Theater era, i recently owned a Yamaha RXV-995, Pioneer 525 dvd player and paired it with BOSE AM5 and BOSE VCS-30 and a cheapo Lexus Digital Mic Mixer for videoke parties. i cant say anything much on the Yamaha they have great decoders and DSP's and Pioneer DVD read almost any disc format, but BOSE! if you have alternative, better listen to another sets of speakers. unfortunately i sold this audio stuff to my friend for only 55 thou due to financial needs. now im back to cheap amps such as Konzert just for the fun side of it, pang harabas kung baga. BOSE are great for vocals but they lack frequencies when you use it on home theater.
anyways setting aside some other issues your opinion and your mathematical computation are great, you have the abilities to analyze such as these, thus putting you at the edge of others. overall you have a great opinion, keep on giving good advices, coz for us audiophile learning from this hobby is a never ending expirience as technology upgrades, i also learned from you, sure on i will read more of your reviews...
more power dude.
