IMHO, as a fellow horn player...

8Ds aren't bad...if you can get one that was made prior to 1985.

Don't look at 10Ds or 11Ds. Great horns, but $$$$$$$$$.

Holtons, to me, can be hit or miss. Heavy, and in many cases stuffy. But if you really look around you can find good ones that play freely.

I have been playing on a Yamaha 667 since 1990. The intermediate version is the 567. Both are good horns...but then again I am biased.

I would also take a look at 6Ds. Great for MS...and will also serve a HS kids as well.

There are other good horns out there that will get mentioned in this thread. Try to take a look at as many horns as you can.

Your millage may vary.