It's all about what you want, really. You can turn your sub level down(on head unit) so that you can barely hear it at full volume, or hear it loud as hell at ~10%. It's however you want your system to sound, just be careful of clipping/distorting your sub.
With that said, I've never owned a JCV h/u, but I've always kept my sub level at 0 and loudness off, so maybe you could start there.