You'll tie your hands behind your back if you buy the amp first.Well, if you get a big Sound Lab, there really aren't a lot of amps that drive that speaker all that well. But it is at the same time one of the most transparent and full range speakers made. If you happen to hear a set that is correctly set up and buy them as a result, to best serve that purchase you have to deal with the limited number of amps that play it right.
Its 30 ohms in the bass; for a solid state amp to keep up with a 200 watt tube amp you need about 800 watts. And it will be too bright...
So in this case, is the speaker the first thing to get or not? It might be if transparency and realism is at the top of your list, and you don't care what it takes to get there!
So its probable that the correct answer isn't something boiled down to black and white!