Ask yourself exactly what it is you intend to do with the new scope and work from there. It's rather hard to answer this question without knowing what your observing desires are. It seems to me that the Pronto and Takahashi are pretty darned similar in size and function to your Vixen. However, in that regard, you might as well get the Fujinon 10X70, which will have about as wide a field and similar light-gathering ability. Plus it is always a good idea to have a nice pair of binocs.
Some purists have it that such a large obstruction is a great sin.
Let me suggest you get a diffraction-grating spectroscope. It is also one of the most colorful, literally, things you can do with an amateur telescope.