While I agree that learning the sky is important, it is time consuming and some observers find it difficult. Hence the large number of nearly new telescopes for sale in the classifieds. If you can achieve this, then I would go for more aperture, at least the 6" dob, if not more. Otherwise you may be dissapointed with what you see. Dark skies help a lot if you are going to manually find difficult objects. I have an 8"SCT and ETX90/EC plus Autostar. The ETX is such a joy to use that I was seeing far more than with my SCT. I solved this by fitting digital setting circles to the SCT. Its a tricky decision which depends entirely on the features you want. (A rather biassed personal view is that a dob is not a good starter telescope, but half the internet will argue otherwise!) Good Luck whatever, Keith.