The overall boot time is crucial for that application.

Ok, thanks for the clarification. I'm still not really surprised that you're getting that kind of performance out of the Pi in general... how fast is your SD card? Perhaps throwing a little more hardware at the problem would help? For example I've read good things about the quad-core 1.5 GHz ODROID-C1, for $35 (http://www.hardkernel.com/).