I moved on to 5 strings after joining up with a jazz quartet, I found the low 5th string ideal for low d's against the g (3rd fret 4th string) also useful to have a low e flat against the a flat on the 4th string. Also I have hand & wrist problems & find as we play a fair bit in f I use 6fret on low b string to give my fingers less of a stretch. Headless basses have always been a favourite of mine (these are usualy 34" scale) Sei's are light as a feather but not cheap, steinberger spirit's are excellent value if you can find a 5 string, the downside of the steiny is the way they hang on a strap, they need a bracket fabricated to put the top strap button somewhere over the 12-14th fret, not difficult to sort out & that improves playability no end. If you fancy something headed I have a warwick fna 5'er going spare as I really don't need 3 basses any more. Moving from 4 - 5strings is not that difficult, initially I gigged my Sei as a four string & gradually added in notes from the 5th string, now I have become so reliant on those low notes & options of other playing positions I could never go back to 4, give it a go, all the best, mike b.