Muddy, I started with a very poor quality $AU200 4" Newtonian that is an absolute piece of junk, and I still had a ball with it. Seeing Saturn through that badly collimated low-contrast scope was what hooked me on visual astronomy. You, on the other hand, have a fantastic scope to begin with. Geez, you even have goto and tracking!
Just check out Mars, Saturn, Venus for starters, and Jupiter when it comes around. Oh, and the Moon of course. Then the brighter DSOs, like M42, the fine selection around the eta carina region, LMC, SMC, NGC 253. Brighter objects like planets might be easier to locate manually through the finderscope (but I don't know if Goto scopes have a "manual" mode
). The two eyepieces you got with the scope sound a very sensible choice.
I suggest you take your time exploring what your scope has to offer and what sort of objects you enjoy looking at, before buying anything else. What would be a worthwhile companion to your scope is a pair of low magnification (7-8x, 10x max) binoculars for getting wide angle views of the sky. You can see lots with binos and you can take a closer look at interesting objects with your scope.
Have fun.
