Makes sense to hold off on the more costly options and start with the ergonomic grips and some long bar ends. To tell the truth I've never used Ergon grips myself. I felt it was OK to recommend based on advice from many respected sources. I've never had serious problem with numbness either, maybe because I use barends and/or gel gloves, the additional positions should help. Think about Wanderer's advice to get grips from Ergon and barends from elsewhere, so you can easily mount a mirror. You'll have a wider choice of barends and you can add clip on drops like his later if you decide you want a lower position for headwinds.

Topeak makes a bar space extender that looks nice but probably only fits well on flat bars. If your bike has sort of curvy bars with taper, it might take some fiddling to get it straight and/or tight.