It depends on what your looking for in an antelope. If you are wanting to field judge and try to hit a specific trophy quality I'd sure want a spotter. If you are ok with just shooting a cool looking antelope I'd go with the bino upgrade and make sure I had a tripod and way to mount them on it. I've heard good things about the Swaro EL 12x50 as a good all around binocular for use with or without a tripod.
I took a relatively inexpensive Nikon ED50 spotting scope I bought re-furbished for around $400 on my last antelope hunt. Even the little spotter was adequate for what I was doing, there was to much heat distortion, dirt, and smoke in the air for a big spotter to do much better. I have a big spotter now, but still like having the little Nikon around for hunts where I don't want to pack the weight of a big one.
Whichever you choose, I'd go with the buy once cry once theory. I upgraded my optics a step at a time and spent way more than if I'd have just bought good ones to start with.