SuedePFlow,
Thank you very much for your detailed post, complete with the speaker driver brands and part numbers that you have tried, and the results you found. Much appreciated.
I don't think the factory box is to be blamed. At some point, albeit for only a short while, the sound from that box was acceptable to you, until a mechanical clearance issue that you successfully identified caused it to fail.
So the most logical and immediate solution that comes to mind is for you to repurchase (better yet, obtain under warranty, if possible) another copy of the original Kicker driver that you liked, and at the same time purchase a grille for designed for it.
Then cut a large circle following the guidelines molded into the trim panel, and remove the factory grille that intersected with the outward excursion of your driver. The new replacement driver will have it's own protective grill that is designed for it.
If you want, you can even paint match the speaker grille to match the interior trim color, if a more factory look is desired.
Alternatively, there is a shallow mount Pioneer 8" sub driver that you might consider trying out. Part number TS-SW841D. This thing only requires 2.5" of mounting depth, and can be in an enclosure as low as .15 CuFt. It has up to a 500 watt power handling, so your 300 watt amp will be in the speaker's sweet spot, on paper at least. Resistance is 4 ohms.
There is also the JL Audio 8W1v2, which is discontinued, but there is remaining old stock here and there. It is also 4 ohms, but is going to require you going back to the MDF faceboard again, as it has a deeper minimum mounting depth of 3.85". By comparison however, the Kicker C8 that you liked is 4.0626" deep, so the JL might not collide with the factory plastic panel at all, saving your factory stock look.
The more I think about it, the more I think you should try that Pioneer. I've read some other posts, but forgot which forum, there are so many, about folks using Pioneer shallow mounts in the factory enclosure.
When reading forum posts, be careful to distinguish between Tahoes versus Suburbans, and likewise for their respective corporate twin equivalents from GMC and Cadillac. As you know, due to the fuel inlet housing, the Suburban box is much shallower where the driver mounts. So anyone talking about fitting 8W3v3 drivers, at 4.63" deep, likely has a Tahoe, or has made modifications that intrude more significantly into the interior clearance outside of the trim panel.
Thanks again for posting, and welcome to the forums. I learned a lot from your post, and hope you find a solution that works for you again, that is more reliable and longer lasting, as well as decent sounding.
One more thing... I wonder if you can borrow another amp, just to rule out the possibility that the amp circuitry is undermining your efforts. It was kind of a surprise to read of your disappointment with the otherwise well respected MBQuart. That made me suspect an amp issue. But I'm not an expert.
Also, have you measured the interior volume of your Sub box? Will you do that as a favor to yourself, and for us as well? We cannot assume that the interior volume of the Tahoe box matches the Sub box. I have the Sub box, but the original factory driver is still well sealed onto it, and since it is in good condition, I don't want to break the seal.
If your box is already a big hole waiting to be filled, then if you measure the interior volume, we can all know if some of these drivers that you are trying are correctly matched to the box. The Pioneer TS-SW814D appears to have quite a bit of latitude in their recommended enclosure size, from 0.15 to 0.50 CuFt. On the other hand, the JL 8W1v2 has a narrowly defined 0.30 recommendation for sealed enclosures.
Keep us posted as to what you decided on, and how it works out for you.
Upon having issues with the MB Quart, I did decide to rule out the amp. I swapped in the Rockford amp from my car and there was no change in quality or output. I tried both amps with the Rockford sub as well.
