Plossls tend to be OK at the longer lengths. The 26 and the 15 should be fairly easy to use. In your scope they will give 38x and 67x respectively and the 9 will give 111x. In most situations you do not need much over 100x and in an 8" pushing much beyond that on most nights is asking a bit.
So I would persist with the EPs you have and try to do as much with the lower power ones as you can. Best thing is to try and get to observing nights and ask to try others eyepieces. In most cases, observers are happy to oblige and it will give you a good idea what works.
I know it is a bit in the future but as you are in Melbourne, think about coming up to the Snake Valley camp, first weekend in November. We are a very friendly bunch and you will get to see losts of scopes and try lots of eyepieces. The website is here
http://ballaratman.wix.com/svaa#!events The other suggestion of the MPAS is good also.
Malcolm