I'd concur with the post that said check out other scopes - preferably in the same location you're viewing from so you can compare.
I too had little frame of reference when I bought my 8" Dob recently (also my first scope). I was concerned about the colimation issue - especially since I was buying a scope that had little after sales support and was relying on the collimation direct from the factory. I was lucky - the out of focus 'bokeh' is well centered around the centre point when I defocus on a star or planet.
I have done all my viewing so far from a garden in a North Western Sydney suburb and even then the views of Jupiter last night - low in the sky and towards the areas of higher light polution (for me) - were stunning. A bit shimmery at times but occaisionly I'd get enough to see two distinct bands of clouds and the four moons. That's just with a 9mm eyepiece with no Barlow lens at all i.e. magnification about 133x. The moon is amazing through this scope - you feel like you can reach out and touch it - it looks like a concrete football
I've also viewed the Orion Nebula and the dust clouds are well defined. The other night I viewed M41 - a nice open cluster fairly low in the sky. Mars is a bit small in my 9mm - really need a bit of magnification.
I think you need to double check with other scopes and get someone experienced to go through some fine tuning with you at your viewing possie (or theirs) - don't give up though - I'm sure you're close to getting some great views - a 12" improvement over an 8" will give you more detail and resolution (my scope is from the same manufacturer I believe (Guan Sheng Optical)).
All the best,
Steve