Speakers:
Aftermarket Replacement Speakers List - The "MASTER" Thread, credit:kaigoss
Underseat Speaker Replacement Info
Custom Spacers by JTSherri
Helpful E-92 Fitment/Spacer/Comparison Thread (plus some MS-8 info)
Musicar NW Drop-in Kits (forum sponsor VP Electricity)
Note: Musicar is now selling completely Plug & Play kits, some of the threads below may pre-date those kits, but are otherwise excellent examples of the quality of their products/integration
Sample of options
Musicar Level I Install and Opinion (Jehnerts and Morel Dotech)
Audio-Systems Drop-in Replacement Kit
BSW
BSW review
Is BSW Speaker Upgrade Worth It?
BSW Stage I Upgrade Review
BSW e92 Upgrade
B-737's review on Rainbow SLC & Profi's
Subwoofers - by Kaigoss (links to later in thread)