Plenty of discussions on the forum about this particular subject.
I have the Bose, its set up - imho - correctly and is more than loud enough, in fact, too loud if pedestrians are nearby, and that's the music not the wonderful Farts and Belches my 718 makes which I prefer the pedestrians to appreciate
I use wireless CarPlay and AMZ music downloaded at best quality available. I mention this also as sometimes playing over the Bluetooth, some systems do suffer - in this one, if It does, I do not notice.
I had the Burmester system in my last car - a Merc convertible - and it was honestly just ok but not worth the extra (by far) outlay, again imho.
Overall, I am more happy with my 718 + Bose (10 speaker, 505 watts) rather than the Burmester (12 speaker, 821 watts).
I do not have any experience on the Base unit but its only 6 speaker and 110 Watts - which I do think is far too little, especially in the Boxster. The jump then from Base to Bose is significant but Bose to Burm is quite small in comparison.
I - again personally - would not worry in the slightest about resale regardless of the system chosen as supplied.
An add here, is Mrs Sub has the Bose in her Merc SUV and its cr@p in comparison to my Bose in the 718. Absolutely no idea why and I have played with all its settings trying to replicate mine but it just does not and will not pump out the sounds in the same way - with this on both the base sounds and the volume to note.
My conclusion with this in fact is the Merc is far better with the Burm and the 718 far better with the Bose.
IF you have the money to spend then of course go for the best you can then get BUT finally, do ask your centre for a demo of all 3 systems in operation. This really the only way to then decide AND then its your chosen spec.
Everything with these cars is a personal choice, seats, colours, trim and materials and sounds is just another one on the list.
Some will absolutely prefer the base unit IF then never really using the sound system for instance.
Good luck in your choices and let us know the end outcome.