The thing I love about a 5 is not so much the sub-E notes (although I play with brass, so they do come in handy), but the fact that I can play across the neck rather than just up and down. I find this very useful. Personally I would definitely stick with the 5. Persevere, it will all come good.
There are loads of 18-19mm spaced fivers around. I believe the Yamahas are 19 or even 20 (my RBX certainly was), my Sire V7 is 18. If they were less than 18, I wouldn't get on with them either.