As far as newts are concerned, the GSO is going to give you the best mirror, their quality in that area is well known. I would go with two mounts, don't tie all your imaging activity up on one mount if you can avoid it. I would forget The 6", minimum should be the 8" as an all rounder. A 10" can be handled fine in an NEQ6 mount for imaging load. I generally prefer an f5 Newt, simply because they are easier to collimate correctly and you get longer focal length than an f4 for not much more exposure time.
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