I would strongly encourage you to play one of these horns before purchasing it. Be very sure to check it with a tuner and ask yourself if it is something you want to live with.
The sound is quite good on the Culbertson although it is such a big sound in my view it defeats the purpose of having an F tuba. Response favors the low range over the high more so than other rotary F tubas. Again.. this runs contrary to the purpose of an F tuba. Finally, the intonation is just plain terrible on the ones I've played. In my opinion the poor intonation makes this horn unplayable.
I would encourage you to to check out F tubas from B&S(my first choice), MW, and Miraphone.
Best of luck!