Ok .... just take make things clearer.... Everything gets used just as much as each other. Xbox and 4K and Apple TV 4K. Only music tends to be YouTube videos and the odd concert on disc. Netflix and NOWTV also via app on tv. I Rarely watch terrestrial standard tv.
im WAY out of the loop in regards subs. I assumed if I connected a stereo amp via optical that had a sub pre out I’d 2.1 for everything. Is that not the case ?
It depends on whether we're defining 2.1 in speaker terms or signal terms.
In speaker terms, 2.1 is broadly understood to mean a stereo pair plus a sub. The '2' is for the stereo speakers, and '.1' is for the sub. You'll find
Hi-Fi speaker kits, and
AV speaker kits and
PC speaker kits referred to as '2.1'. Some of these systems will only be used to play music (20Hz-20kHz), whereas others will have mixed use for music, TV, films and gaming.
Looking at audio signals though, 2.1 has a different meaning.
The 2 stands for Left and Right full-range audio (20Hz-20kHz generally, though dance tunes can go lower in bass). The '.1' now refers to an additional frequency-limited bass effects track. The frequency range is from 3Hz to 120Hz. This has nothing to do with what's happening in supplementing the bass from the main stereo pair. You'd still hear the bass thumps of the T-Rex stomping about even without the LFE track. But pass the signal through an AV receiver, and hook up a sub big enough, and you'd feel those stomps as well as hearing them.
Coming back to your question then, where you said "
I’d 2.1 for everything", then I can say for certain that the sub would always be filling in the bass for what the main stereo speakers can't do. If that's what you meant by "2.1" then the answer is yes. This would be the case with a stereo amp with sub out.
Should you decide that an AV receiver meets your needs better, then the sub will fill in the bass as above, but it will also play the LFE track of any source signal such as a 5.1 movie from Netflix or Apple; and if any of your games make use of LFE too, then the sub will play that as well.