@BobK stated in his original post that he is going with a modern stereo. If you look at the offerings from XKs Unlimited for ideas, you’ll see the whole gamut of retro-looking stereos, faceplates, knobs etc., and, of course, the Kenwood speakers that fit the E-Type console.
When new, my car had been fitted with a monophonic AM/FM radio with a single speaker. The other factory options were a blanking plate, and likely an uprated two speaker system. 8-Tracks had not been invented yet. Cassettes had not been invented yet. True stereo in cars had not been invented yet, to my knowledge. All this is to say that in a loud sports car like the E-Type, the sound sucked, and at speed with the top down, you could barely hear it.
When my dad and I acquired the car in 1971, I installed an early model cassette player, “Carsette by Tenna.” It had its own amplifier and was too big to fit in the console, so I cut a slot out of the fiberboard glove box cubby, shoved it in and wired it up to some outboard speakers, which I set behind the seats. I applied electricians tape around the hacked cubby fixture to make it look “pretty!” (Note: I had just graduated high school and didn’t have much in the way of funds. My dad was my partner in the neglected car which had been a high school shop project.)
At the time, the setup was the best offered. It worked fine until the player was stolen a year later–the perp sliced a hole in the convertible top.
I had also wired in a 1/4 stereo headphone jack (the little 1/8 kind wouldn’t be invented until Sony’s Walkman ten years later.) With those big headphones on at speed it was quite the surreal experience! And dangerous, yes! Ahhh youth…
When I restored the car in the 80s, I installed a blanking plate, as I showed the car in JCNA concours for a few years, and an aftermarket stereo will cost you major points.
Beginning in 2013, I modernized my car sound, tweaked it over the ensuing years, and finally have an excellent solution:
Hidden stereo amplifier from woodyscustomshop (2013)
Kenwood KFC-1664S speakers with speaker rings from XKs Unlimited (2013)
Kenwood KSC-SW11 Compact Enclosed Subwoofer from Amazon (2016)
Aston Innovations SoundTek A2+ remote Bluetooth controller that connects to my smartphone automatically when the ignition switch is turned on, also from Amazon. (2020)
Note that the controller can be tucked away and the subwoofer unplugged and removed for show; there is no evidence of a stereo in place.
I think the sound is as good as it gets. Photos above in my earlier post.