I don't have to. I'm not claiming old school is more reliable. Im actually on the other end of the spectrum, saying there's not enough data to make a determination. Im also not the one claiming that today's amps won't be working in 15 years.I own a few ppi, pg, and zapco amps. Planet audio and us amps were budget amps on their best days. The fact you now find them high end shows the absolutely laughable amount you actually know about what you speak. Us amps were current hogs, but good amps. Pg is currently a completely laughable product line up minus the elite line, which is hardly a value driven consumer line.
I'm really glad you worship at the altar of zed. I'll take my d7s all day over anything he's ever built, but that doesn't mean his products aren't ok.
If you want to compare them to amps of today, sure, as long as we compare like for like. Mosconi, tru, brax, etc. are completely comparable. If you want to spend less, There are options there as well.