I just signed up and started a thread in the New Members sections, but I'll add to this thread in case anyone finds it helpful.
Some background first I guess. I've been a professional audio mixer for over 20 years in NYC. I rarely spend too much money on sound systems because I could spend $10,000 and still not have what I'm used to hearing everyday so why bother haha. It's a sad joke in my business. I do love good sound in a car of course though. In the 90s I had a custom system installed in an IROC, but since then I haven't bothered going that route.
I currently have a 2007 G35x and for a stock system, I love it. Nowadays, Infiniti likes to say it's like being in the front row of a concert, but in 2007 it was something like Studio on Wheels. I've read many negative reviews on the Studio on Wheels systems, but at least in 2007 I think it was a perfect description. It might not have been bright enough for some, or maybe not thumping enough for others - basically not HiFi enough for a lot of people which I totally understand, but I felt it was a very good representation of flat studio monitors. I can throw mixes at that car and it will feel fairly "true".
That being said, last year I almost bought a Q50, but I again read reviews on the Bose system that weren't that great, so I went to a dealer with a playlist of a wide variety of 15 songs and asked to sit in a car by myself and listen. I spent close to an hour doing that with the different DSP settings on and off. I was so turned off by the sound regardless of settings that I decided to keep my G. For me, the 2016 and earlier Q50s simply sound terrible. I started to consider buying preowned and dedicating a large chunk of change to a full aftermarket install. I gave up on that though and waited.
Then the Q60 was released. My last kid is almost out of the house and I can go back to driving a coupe - plus I heard it was a brand new Bose Performance Series system. So I had to have a go at it. I think I spent more time listening to it in the parking lot than I did test driving it, which I'm sure many will find ridiculous haha. Anyway, even though I spent around 20 minutes listening to it, all I actually needed was 10 seconds. It was immediately noticeable that it sounded better than my G and made the past Q50s sound like a toy. I don't like messing with treble or bass so I had them all flat, though in a perfect world I'd have an EQ in any car and tweak it with the correct software and mic. It sounded big, loud, fairly true and just great in general with low distortion. I didn't even mind the DSP settings on nearly as much as I did in the Q50, which I thought just made a poor sound system even worse. I was really impressed with the Q60's Performance Series and have no want at all to spend more money on a custom system. I put down a deposit last night on a Q60 and can't wait to be rocking' down the road in it.