Well almost all the greats from 20 years ago have fallen. Phoenix Gold (though they've had a few decent things), PPI, Soundstream, MB Quart, Hifonics, US Amps, Lanzar, Crunch, US Acoustics (Pretty much all the old Zed made brand names were sold out, though Zed is designing great amps still for Focal, Mosconi, and under his own brand name) Orion (though they're making a comeback perhaps). Rockford Fosgate is still the same as is Kicker. A/D/S (used to be made in Woburn) is long gone, Xtant is gone, Linear Power gone, Boston Acoustics used to be made in Peabody and has fallen some.
For loudspeakers, TC sounds has come and gone 3 times (their drivers are still excellent if you don't mind buying used), Adire Audio is gone but about to come back (also excellent drivers). JL is still great IMO. JBL/Infinity is great price and performance and Alpine Type R is as well. Alpine Type X is premium price and quality. Most people who care about high-end components buy raw drivers from
PartsExpress, Madisound, or boutique companies and cross over via the head unit (those have come a long way in processing power and performance and the prices have got insanely low).
Power is cheap and comes in small packages, 1200w woofers can be had for little more than 200$, and while they aren't terribly efficient can function in small-ish boxes. Almost every high powered subwoofer these days is engineered to function best in ported box so ported is pretty much the conventional wisdom these days. "Stiffening caps" have been proven useless or worse but new "ultracapacitor" technology is useful but scary and a bit expensive.
Weldingsupply.com orange "ultra flex" cable is great stuff fairly priced and made in USA. Knuconcepts (SP?) is a popular choice for cable and Sky High also seems good. I buy a lot of cable and distro stuff from Darvex.com, their selection is all good quality and priced fairly.
Biggest car audio event of the year in the northeast happens the end of this month:
Sanford Sounds Show and Shine
Pop by and see what's new for yourself. Plenty of other types of cars at the car show so worth a trip up to Maine for the day.