Noise is a very personal thing neither of my ZTs were particualarly annoying with 18" wheels on but otoh the engines were making the right noises to drown it all out
My 75 CDT is very different though originally it had Crowns and 15" wheels
I bought the 16" Seven spokes from Ebay with brand new tyres on them for £190 and I used them quite a bit at first. I did not notice any increase in noise. Now I have the Serpents I only use the 16" wheels in the winter as they are so much easier to clean.
As soon as I fitted the Serpents I noticed three things
1, A slightly firmer ride
2, Slightly more grip or less roll depending on your point of view
3, A lot more tyre roar from road noise, especially on concrete.
I have since had two different brands of tyre on the Serpents and swapped brands from back to front and the car remains noticeably noisier with them fitted, not annoyingly so but I do prefer the quiet of the smaller wheels!
I reckon the 15" Y spokes would be smart and quiet and 15" tyres are nice and cheap compared to 17" and 18" ones!