Thanks ahbe. It seems that some subset of the speakers (presumably some portion of the mids) were simply not firing at all after the 46 update for me. A full reset seems to have solved the problem though.
Thanks NY_Rob, I did check the EQ and try moving some of the ranges up to see if it helped, but it didn't seem to make much of a difference (other than making everything sound awful, lol). Someone on the subreddit (where I also posted this) said they had some speaker issues after the recent...
SOLVED: Apparently the 46 update broke some portion of the communication between the truck and its speakers in this case. A full restart has solved the issue and everything sounds great again. Thanks to those who read/responded.
I tried finding a thread on this, but was unsuccessful, so I'll do...