I run "oldschool" amps but is mainly because I can do it for less money than an equivalent new. Adcom has not let me down. Luckily you can pick them up cheap anymore. Back in 95 my 4404 would have been over a grand, now they are less than $400 and I would put them against any 75-100x4 a/b in output and transparency. It has ran my entire car in the past and currently will just run front stage. I just picked up An older usacoustics for sub duty. Once again the price was right and I refuse to run class D.
I have stayed away from stuff like Old RF, PPI , LP, and SS for the most part because I feel for the most part they are overpriced due to collectors feeling the need for a showpiece. Ive had a few over the years but as the prices went up, I became less impressed. I still feel the Kicker ZR circa 99 and First 2-3 generations of MTX thunder and blue thunder are about the best deals out of anything. I have nothing against new amps, there are plenty of quality ones. Main reason I stay away is 1.) fear of change to an extent. I know about amps till 04ish, after that it is a mess of good and bad. The reputable companies are hardly that and there are a lot of small companies that are building quality. Hard to tell what is what though since the same board will be in 8 amps ranging from $150-$400. and 2.) there aren't as many affordable larger class a/b. My method can yeald me 800-1krms a/b for less than $200.
Not all oldschool is that great anyway. There was midline and crap then just like now. I see crossfire brought up a lot. They were pretty good amps but they were entry line and in my experience drew an excessive amout of current. USAcoustics is another. Zed was not an end all of the ultimate. USAcoustics were a mid line product that did advertised and sometimes more. I've had some usa and usx over the years. None let me down but none made me tear up either.
As far as speakers I feel that they are better than ever. There are so many small sub companies making drivers to do whatever you want so that is covered. There is more information than ever about how to make $75 in drivers from PE or madisound sound better than a $500 component set which is a segway to my next opinion.
With real processing available to the masses, active setups can be done affordably. The days of 3-4 large processors are over. Even people running pro audio gear can just rock one Behringer piece that does it all. You can even pick up head units that do it all for less than $200 used. You couldn't do that in 99.
As far as head units themselves go I do believe the 90s did see some of the best. However I feel in a non competitive environment (driving) the good of today can hold a candle to the best of then and you now can play other formats and do processing in one unit, eliminating cables, components, and noise.