It all depends on what you want to look at. Your 10" Dob is great for deep sky objects, but not very portable, and not ideal for planets. A refractor of at least 90mm is nice for solar system objects and splitting doubles. A small Mak-Cass, like an ETX90, is great to take with you when you don't have room to take a telescope. A medium size Mak-Cass, like an Orion Apex 127, is great as a portable scope that can do almost everything: great for solar system objects, doubles and star clusters, and you can even see some of the easier galaxies and nebulas. But don't expect any of those to show deep sky objects the way you are used to seeing them in your 10" Dob. (Btw... I have each of those scopes).
...John