I have the Televue 76 as well as a Pentax 100 ED spotter, both have replaceable eyepieces. The Televue 76 is nice but it is as heavy as my Pentax 100ED. One thing about spotters versus astro scopes, the spotters are build with materials to keep the weight down.
The Televue will be quite sharp when using a dielectric diagonal. But then the image is inverted. Once you add the image erecting diagonal (I got the top line Baader), you bring the image quality down to that of a good spotting scope. So for strictly viewing erect images and mobility, the spotter still wins. But if you go into binoviewing, squeezing the last drop of image, or photography, the astro scope wins so long as you don't worry about mobility.