Re: New Horn
The late 1930's and early 1940's Conn 10M Tenors are among the most highly thought of vintage horns. The 10M lost their rolled tone holes in 1947, if I recall, but still are well thought of through the late 1950's models. At some point in the 1960's Conn, as well as most American manufacturers, started downhill.
Around this same period the Buescher pro line tenors are quite good. The Martin Tenor models from the late 1940's through the early 1960's are really fine horns. The early King Zephyr Specials and Cleveland made (through the early 1960's) King Super 20 tenors are very good. The Super Balanced Action and Mark VI Selmers from the late 1940's through the late 1960's are the most expensive vintage saxes generally and are very highly regarded.
You can go to saxgourmet.com to get some idea of values in near perfect shape.
As far as new horns, you need to go to a big music store with your own mouthpiece and cleaning supplies and play a bunch of them - perhaps even compare to some vintage models they might have.
The Yamaha YTS-62 from the late 1990's was their pro line horn and can be had in great shape for less than $2500 - perhaps far less. This horn is easy to play in tune with nice modern keywork. You'll find the sound a bit brighter than most vintage saxes, I suspect. The newer Yamahas and Yanagisawa saxes are a bit cheaper than the new Selmer Paris models, I really don't know how the Keilwerth pro line is priced now. It's just a matter of preference. I would greatly prefer a Selmer Reference 36 in brand new horns, but you might not. They all need to be set up right though.