Hey folks,
I'm going a very different route with my 986 stereo overhaul, but this new all-in-one powered subwoofer/5-channel amp/signal processor by Alpine for $600 might make for a great backbone for a stereo overhaul of the crappy/worn-out OEM setup these 986s came with originally.
https://www.crutchfield.com/S-pLREPe6QRBc/p_500PWDX5/Alpine-PWD-X5.html?omnews=12547604
Here are the dimensions: 9-5/8" x 3-1/4" x 13-5/8"
Vs. Alpines similar powered subwoofer (only no extra channels and signal processing): 9"H x 3"D x 13-1/2"W
Cheers!