opinions on wiring tweeters differently

Not usually, no.

Your theory about gain setting is dead wrong.  You are probably clipping your amp without detecting it.  Have you scoped it?  If you need to attenuate your headrest speakers (which I would remove if I was designing your system as they will only do harm to your overall performance) then use your L-pads on THEM.

You need to pad your tweeters so they match the sensitivity of your woofers.  Using a L-pad is a cheap and dirty way to do it, sure, but it will always (always) add noise and shift the Xover point since L-pads are generally inductive loads.  You should calculate the amount of pad needed and use a fixed voltage divider built from non-inductive resisters.  Are you still using those overly complex 4th order crossovers you posted a while back?  They could be part of the problem as well as they simply contain way too many elements to be reliable unless you used VERY high quality (read: expensive) parts to build them.

Give me the makes/models of the two speakers you are trying to use as your home-made component set and describe their relative mounting positions, and I'll design a crossover network for you to try.

OK, first off just looking at the two drivers you've chosen, they are a very bad match and that could be part of your frustration.  I can't put together a good crossover for those two that I would recommend to anyone.  What is your crossover frequency?  I would not recommend crossing that Dayton woofer any higher than about 1500Hz, and the little Dayton tweeter is not much good below 3000Hz.  So you have a big huge natural hole in the response, right in a critical frequency band for music for speech, and forcing the tweeter to play too low will eventually destroy it and make it sound very ragged while it dies.  A much better tweeter to use with those Daytom woofers is something like THIS.  You have to pay a bit more than $5 to get a tweeter that can reach into the upper midrange like that Dayton woofer requires.  Or get a better woofer that can be crossed up around 3KHz, maybe like THIS one (which I use in my home.)

Also you say you are using electrolytic caps in the crossover.  This is generally a no-no unless you are using very expensive bypass caps, and even then electrolytics can cause all sorts of sonic issues not the least of which is high frequency harshness and distortion and a very thin, shrill sound.  You need to use good crossover caps, metalized poly at the least, like THESE.  A good passive crossover generally will cost more to build than the drivers it is controlling.