The Vortex Skyline ED is a great choice. I love the one I got. If you go to this link they have a killer deal for the whole digiscoping setup and I think it is even free shipping.
You may want to look at the Kowa TSN-601 (angled) or TSN-602 (straight) for $810 from the Outdoorsmans. The 60mm scopes are small and lightweight, and one of the best values in the spotting scope market.
For $115 more, you could also get into the 66mm Kowa...
I have the Pentax 20-60x80 ED and love it look it up on betterviewdesired they did a review a few years back and it became their benchmark in an 80mm scope they liked it better than the Euros of the time (pre-HD scopes from them).
I haven't had an opportunity to compare to any of the Euros but to my eyes it was better than the Nikon and has the ability to use a huge variety of eyepieces designed for telescopes of which most experts say Pentax makes the best.JMO well worth $1000 pricetag even though its a little more than you want to pay.