Meridian offers some amazing models. Ergonomically and sonically superb, exceptional build-quality, lots of customization options. I have a Horizon 33" fretless 6 which I love. Top end of your budget but well worth a look.
Currently strung with a low B. It looks like D'Addario does offer high C strings so it could be changed to E-C. (Stands to reason as NS does offer 6-string EU and CR models). There might (or might not) need to be adjustments made to the bridge and nut slots to accommodate the changed string...
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