Re: BFL Single and BFL mini-rig seems to have inferior performance
Maybe he realized that there is no way to compete with BFL and wants to get a job there, by showing how 'smart' he is. Otherwise, he'd just make something better himself 
As for Spartan solution - it is already fastest, and if yohan's prices for board combined with my bitstream price per Mh/s would be $0.53 / Mh/s for FPGA (1200 Mh/s for $640). This already beats BFL prices. If my licensing per-spartan would be applicable ($25 per chip) - then it would be 1200 Mh/s for $740 - $0.616 - again beats BFL. But - yohan prefers 840 Mh/s :-) While our capabilities do not allow to deploy quickly and cheap solutions.
If you can do this, why not use the tricone model? Publish a bitstream for cairnsmore that extracts a commission and go straight to the end user. Every single person would use it. You could direct 200mh/s? to yourself and make your goal of $25/chip in no time. There are hundreds of these ready to go.