I don't have Pi's yet but I plan to build some to check out low powered SET or PP amp's in the future. I run a set of Newform 645's that I DIYed.
I also love the sound of some of the vintage jazz recordings.
A friend was over the other day and I put on an old Miles Davis CD -Cookin With the Miles Davis Quintet I think it's called. This is recorded in Mono and we were both impressed with the realism.
One of my personal fav's is Sinatra Live at the Sands recorded in the 60's. If you like big band sound try this one. The monologues are also an insight into the culture and values of the time.
Belefonte's 2 Carnegie Hall Live concerts from 1960. Lots of depth and size in the sound stage.
I also have that Getz Gilberto vol. 2 CD. I must go back and have another listen. I didn't think it was a very good performance when I first listened to it. Time for another listen.
Shirley Horn I love Paris- I really like this CD. It is another live recording.

Happy Listening
Brian Pugh