First, in a post earlier today, I meant "ground-based," not "groung-based."
Second, do you mean the 8" Schmidt-Newtonian or the 8" Schmidt-Cassegrain? There are two 8" scopes in the LXD-55 line. The 8" f/4 Schmidt-Newtonian is good for deep-sky work. The short focal ratio makes the image bright. However, it also has a short focal LENGTH. The focal ratio determines image brightness for a given object viewed with a given eyepiece (or imaged with a given film or CCD exposure). The focal length, by contrast, determines the object's apparent size with any given eyepiece or film frame or CCD image.
Because the Newt has a short focal length, you'll need a high-quality Barlow (or better yet, TeleVue Powermate) to get the magnification you want for planets, but the low-power deep-sky views should be grand.
Although there's no such thing as the perfect all-around telescope, an SCT comes closest. At f/10, it is a good planetary scope. With the f/6.3 photo reducer, it becomes a good deep sky scope. The photo reducers available for the ETX line just aren't the same quality as those available for Meade or Celestron SCT's. If you can afford it, go for the SCT. If cost dictates a choice between the 5" ETX or the 8" Schmit-Newt, the Mak may be better for planets unless you're willing to spring for a top-quality Barlow, because the Schmidt-Newt has such a short focal length that its magnification will be too low even with the highest-power eyepiece in the Meade deal. However, the Schmidt-Newt has a mount that can be marginally forced to function for deep-sky photography, whereas the ETX simply does not.