Besson?
James....there are many reviews of Besson horns (the 2051 in particular) here on Dave Werden's site. Go back to as early as 2007 to catch up on the feedback. The Besson horns are great. Since late 2006, they have been built in Germany instead of England and the quality is quite good. I own one of the early production 2051 horns, completed in January of 2007. It is definitely one of the top horns you can purchase.
But at the $6000-$7000 pricve point there are other fine honrs as well including Sterling, Mirraphone, Meinl-Weston, Yamaha, Willson, and others. I happen to own and play a Sterling Virtuoso as well as the BEsson. Read up on the many detailed reviews and feedback sessions here and you will be able to educate yourself. However, if you decide you want a Besson, it is a fine choice.
Now...do you know where you will be going to college? Have you contacted your new euphonium teacher at that school? You should do this BEFORE you purchase an instrument. Often, your teacher will have experience and feedback for you on what choices may be the best. I strongly urge you to contact the folks at your college (assuming you will study euphonium there) before you make a purchase decision.
Doug
Adams E3 0.60 Sterling bell - Prototype top sprung valves
Concord Band
Winchendon Winds
Townsend Military Band