I'm an industrial designer myself, and i take it you're doing you research for a product to design for your latest project.
Your biggest mistake is thinking timeless design is highend, its not, when it comes to audio design emotion is key.
Brands such as Sugden, B&O, B&W, Klipsch, Tannoy and many more, they all carry long history's within the brand.
Tannoy epitomises this to their very core, ever wonder why people refer to the sound system in shops as the tannoy system "put a message over the tannoy dear" its the same reason we all refer to vacuum cleaners as Hoovers ( though the only vacuum we call by its brand name these days is dyson). Their very name is timeless they're watershed brands. Hifi is as much about the brand as it is about the piece they design.
NAD for example paved the way for affordable integrated amplifiers that sound fantastic back in the 70's
Sudgen are considered the father of class A amplifiers back in the 60s
Sony gave us the legendary walkman and has a brand language that really is just incredible all by itself. Sony really knows how to market a product lots to be gleaned there.
The first apple iPod absolutely legendary device that brought a company back from the brink of bankruptcy, and the branding/design language that evolved from that shaped the company moving forward!
Modern brands such as Sonos are going be long remembered for changing the industry landscape as they were the first to see the potential of smart phones and devices doing away with the humble control interface of old and utilising the UI of a phone/smart device. And there are still among the best on the market.
Then you have devices such as the Chrome cast audio and the Chromecast protocol. Its not really about the device at all! This will go down as a watershed product for media consumption in general! perhaps the future of hifi is virtual and software with clever AI and wearable tech of some kind. Bone transducers that vibrate the very body. This tech already exists and its cheap!
heck, Spotify/iTunes has done more for the hifi market in 15-20 years than the major traditional hifi brands have done themselves, brands such a Sonos wouldn't exist without them.
Traditional hifi is dying making way for smarter more connected devices, devices that are almost unrecognizable from as little as 20 years ago.
If you want to look at it from a pure aesthetics point of view, and though they divide opinion, Chord has a vary interesting design language along with Devialet. But as a project that would be boring wouldn't it!
I'd say you have picked a very difficult market to tackle for a university project as they always want to see something new in your presentations, the easiest way for you to design your next product is to pick a brand and design your hot take on where that brand will be in 10-20 years from now and incorporate their history somehow in the design. Seymour Powell the poo out of it if your if you're any sort of industrial designer you'll know who that is.
Have fun with your new project