Matt-
I try to strike a balance in my practicing. There are some nuts and bolts things that we, as trumpet players, have to address. That's what Clarke, Arbans, Goldman, etc. are for. Then there are the things that all musicians need. Bach gives you that, but you can also find great music in the etudes of Charlier, Bitsch (if your ear swings that way) and Tomasi (I've performed the lesser known of his 6 Etudes in recital). A few weeks ago I started making myself warm up every day by doing a half hour consisting only of Clarke and Bach chorales (just playing individual melodies). I'm not sure if it's made me a better musician, but it's made me a happier one.
Sigmund Hering's "Bach for Two Trumpets" is absolutely pheonominal. You can find it
here, although I'm not sure if they ship to Germany. Also, I wasn't able to find a link to the sheet music, but David Cooper has transcribed all 6 Cello Suites for trumpet. They're a blow, but absolutely playable. I think you'd enjoy them!
-Jimi