Guy,
Slow down!!
If you have just got your dob spend a lot of time getting to know it and your observing style BEFORE going down the accessories path otherwise you will end up with lots of expensive paperweights.
At present, if you have money burning a hole in your pocket, get yourself a cheshire eyepiece and laser collimator so you can tune your scope to get the best views available under your conditions.
A good barlow, like the Orion Shorty Plus would be a great addition soon as well.
Worry about eyepieces later....................
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