Those days are not gone, just ...evolved. I saw Smashing Pumpkins at the Garden several months ago. Not only was it thunderous ( I had ear protection in) but the light show was INSANE. I have never seen anything that bright. Good to have Jimmy Chamberlin back.
You still live in the Boston area?
The reason to use subwoofers particularly Dead Heads is to be able to create that concert feeling at less than ear shattering levels. They allow you to EQ the bass without affecting the main speakers. To do this a two way crossover is mandatory. Digital bass management is the best thing that has come along for subs since their introduction back in the late 70s. There are units from MiniDSP and dBx that are relatively inexpensive. A great inexpensive way to get into subs is to buy Dayton Kits from Parts Express. Dayton makes great sub drivers. Their kits perform as well or better than 90% of the subwoofers out there. They won't be as fancy looking, but what is the mission?