I just bought the Weaver Classic Spotter 15x45 60mm because it was on sale. Do what the others say: go to a gunshop, Wildbirds Unlimited, camera shop, etc. and set up several spotters. TAKE THEM OUTSIDE, don't just look at some bird mount on the other side of the store, even if its a huge store, you're not going to get a good comparison of light gathering abilities, etc. The other side of the store is only a few hundred feet away at most. If the store wont send someone out with you and several tripods, shop elsewhere.
I compared the Weaver to the Burris and thought they were about the same, so went with the lower price (need to save up for some sweet binos).
Later, I went to WildBirds and set my Weaver up next to the Nikon XL and several others. The Nikon XL is better, in my opinion. Its phase coated, light and clear. You can get them used on ebay or at
www.samplelist.com (full blown outfit with tripod and case on there now for $400, good luck matching that!).
That said, I'm really happy with my Weaver and will use it until I can afford a Leica, which means never.
I went to a used camera shop and found a used lightweight tripod with a light/small ball mount swivel on the top, great for packing.
Good luck.