G'day Stephen
Welcome to the forum
For planetary observing through my 10" dob (my first proper telescope) I originally purchased a 5mm TeleVue Radian
http://www.bintel.com.au/Eyepieces-a...oductview.aspx
Which at 250x magnification (focal length of scope divided by eye piece focal length- 1250/5) only gave really good views if atmosphere conditions were really steady. About 10% of the time I had the scope out.
So I then purchases a 7mm TeleVue nagler
http://www.bintel.com.au/Eyepieces-a...oductview.aspx
Which at around 180x magnification gave good views for most conditions at the expense of smaller image scale.
Now these eyepieces are expensive but, I have collected them over a few years and there are even more pricey variants. There are several alternative brands available at varying prices, you may even pick up eyepieces in the Ice Trade classifieds.
It would beneficial to track down some guys close to you and have a look at the gear they use. (I think there are a couple of amateur astronomers at your local Camera House)
A good quality eyepiece will last you a life time. A bit like having a decent sound system then having crap speakers.
Of course nothing will give you decent views if your scope isn't collimated properly. (alignment of the primary and secondary mirrors). Have a look at this from the Andysshotglass website
http://www.andysshotglass.com/Collimating.html
I also have a 13mm TeleVue Nagler
http://www.bintel.com.au/Eyepieces-a...oductview.aspx which gives wider views (In my opinion is an exceptional eyepiece). It could be used with your barlow....
There is a lot to digest and everyone one has a different opinion....
Good luck