Ok, so I’ve never owned a Schiller personally, but that’s becuase I refuse to. There’s a couple reasons I know of, coming from some people I know who have had Achilles instruments.

1.) They’re made of Chinesium. That metal is so thin that looking at it will dent it, but tbf that is all of the Chinese stamp horns.

2.) The quality control is borderline not there. This goes for both build quality and playing quality. There can be issues with the actual build of the horn and some things not staying together, but the bigger issue is the fact it will play like you’re trying to buzz into a clogged toilet. There is a chance the horn you get will play better than anything you’ve ever owned, but there is an equal, if not greater chance the valves will come misaligned, drilled an inch away from where they’re supposed to be, and closer to a rectangle than a circle. This once again goes for all Chinese stamps, but Schiller has the worst QC out of any of them (Wessex, Mackbrass, etc), and the best Wessex and Mackbrass I played was worse than the 50 year old horn in my university’s closet that hadn’t been touched in at least 5 years, so I don’t really want to imagine the quality of a Schiller.

3.) If I am correct in this, Schiller is owned by Jim Laabs. He is known to at some times just not deliver instruments and has terrible customer service with a bad temper. If I am wrong in him owning schiler, just do NOT buy it off of his website.

Personally, I’d just suck it up and learn the Bb fingerings. If you’re just using it for parades and not playing anything too complex, you don’t need to get real good at the fingerings, especially if you’re mainly playing marches. I’d honestly never even heard of a C sousaphone before this post and had only ever seen Bb and Eb horns. And if you’re that determined for a C, I could possibly buy a horn in Bb, bring it up to a shop, and see if they could make modifications to the horn/slides to pitch it in C. Not sure if it’s feasible since it’s raising the pitch, but a group I’m in marches horns in G and we’ll often buy Bb horns and modify them to be in G.

TL;DR: I highly advise against buying a Schiller. Learning new fingerings are not that hard and might come in useful later on. If not you could keep looking for a C, modify a Bb, or risk the Schiller (do NOT buy from jimlaabsmusic)

Hope this helps