I feel your pain. To have a top-quality audio system, it's not easy to keep the car light.
Things that help:
- Amps with switching-mode power supplies like Class D (adds noise and limits upper frequency range)
- Amps with minimum amounts of power headroom (adds noise, runs warmer)
- Speakers with Neodymium magnets (costs quite a bit more)
- Reduced driver count (requires more EQ and adds intermodular distortion)
- Reduce wire gauge and length (adds resistance and current draw)
- Minimize sound deadening (more road noise and rattles)
- Run compact, high power subs (less cone area and low frequency extension)
Many of us 86ers appreciate that the car is light and fun... but we also recognize that music is a priority worth compromising for. Not everyone has this opinion, and I can respect that.
That said, my SQ setup is going to be pretty stinkin' heavy. Even if I can design a removable box and quick-disconnect amps... it still adds significant weight.
7" woofers = 5 lbs/side
2" midranges = 1 lb/side
1" tweeters = 0.15 lb/side
10" subs = 22 lbs/side
4-channel amps = 21 lbs x 2
mono amps = 10 lbs x 2
infinite baffle = ~15 lbs
wire = ~20 lbs
Total = ~150 lbs (121 lbs removable)
Weight-to-power (stock): 13.81 lbs/hp
Weight-to-power (w/stereo): 14.55 lbs/hp (5% increase)
This is still better than a Civic Si, Mini Cooper S, and Mazda Miata... for some perspective.