Since you asked where you might have gaps in your car list: Track toys. The mental model here is the Caterham 7 - cars that someone might buy if...
LFE, or Low Frequency Effects, is a dedicated channel for bass effects. These tend to be felt more than heard, and so they're routed to either...
iRacing has a very good internal LFE subsystem. It definitely has some limitations (most notably single-channel), but out of the box, it works...
Separate names with a comma.