When you talk about speed you must mean hills right?

The aero benefit of a roubaix to a crux is a total non issue as even the best aero frames out there only provide a very small increase in speed. There was a thread about it but the difference to a normal frame was indeed small. The roubaix is not an aero frame, nor is the crux so one would assume the actual difference is actually too small to measure. Also the crux does aero fork blades so HAH to you

Secondly, the weight of a bike is in the most part not in the frame. You should know this. As long as the bike weighs somewhere between 6.8-9kg I find it acceptable.
6.8 = expensive
9 = affordable
That crux is in the region of 9kg mainly due to entry level components and selfbuilt bombproof wheels. I could drive it down to 6.8kg if I had the money/interest. I don't.

I kinda get the feeling you actually believe you can buy speed. you can, of course but that would require skinsuits, aero helmets, shoe covers etc. even on normal day to day rides. I find that too much of a hassle. Maybe I'll use that stuff when I start doing triathlons but until then I try to keep it simple.