FWIW, I test drove a LEAF with the Bose package when I was shopping for mine and I wasn't impressed. It sounded only marginally better than the stock radio. The mid-range was alright, but the tweeters are rather muted - I prefer them a bit crisper and brighter. The lower range, handled by the woofer in the trunk, sounds pretty mushy to my ears. I'm sure some people just crank up the bass and treble, which does improve things somewhat, but to my mind a "premium" audio system should be more responsive at flat levels. Given the less than stellar Bose "upgrade", I was pleasantly surprised that the stock audio isn't much worse.
I guess it depends on your budget, but I find it's not worth the money to rip and replace everything.
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
1-1/4" Curt #11396 hitch
After market, DIY LED DRLs
LeafSpy Pro + Konnwei KW902 ELM327 BT OBDII dongle
Loving my first BEV