It definitely sounds better than the standard 6-speaker audio system, which is actually pretty decent for a standard setup. I rent cars several times per month for work and the basic Mazda system is as good or better than anything you'll find standard in any other mid-size sedan.
The 11-speaker Bose Centerpoint Surround Sound system is a substantial upgrade and well worth the cost. For $1325, you get the Bose audio upgrade, Power Moonroof and SiriusXM sat radio (on the Touring model).
I will admit that the similar 11-speaker Bose Centerpoint Surround Sound in my 2012 CX-9 GT sounds slightly better overall. It might have more powerful components (beefier amp and/or sub) or it may be due to speaker placement and a better interior acoustics??? Either way, I'd recommend the Bose upgrade on either!
In comparison, my 2006 Mazda3 had the Bose audio upgrade and I was not impressed by it. If I could have found one without the Bose/Moonroof Package back then, I would have went with the standard audio system. But the newer ones are a lot better, IMO.