I've seen more than a few, very high end, 6 string bass just sit around in shops. They are beautiful, hand made instruments. But they just sit for almost years, it seems. I've found three 6 strings basses lately that I thought were extremely playable and with great tone. I'm actually seriously contemplating a Fodera Imperial Elite 6. I've never, ever found a need for a C string but I'm thinking that I might just go for it anyway. Funny but I've just not been really keen on single-cut basses for that matter. I might be making an exception, though.