Originally posted by Theo Wizzago
I'm talking more like speed 30-50... not the 70's posted about. Hope that helps better define the question. 
I've seen some 35-50 speed DTs and they were pretty awful.
I think you need to be at least in the mid 60s for decent results.
The question used to be whther spending above 68 was worthwhile...it definitely has always seemed like getting to 65-68 was a good investment.
It used to be that spending above 68 was a pretty marginal return compared to other investments....but now that 1450-1500+ points builds with 4 AEQ are possible, I think the bar may have been raised on the best speed investment.
I still think that ytou can build a really excellent run-focused DT with speed well below 80 however...probably 73 or 77 speed is a pretty good place to end up. But I do think 85ish speed is potentially wothwhile, even for a run stopper.