After months of work, finally I build a FPGA mining cluster using the board "Icarus".
each board has 2 XC6SLX150 -2FGG484I on it, generates a 380MH/s hashing power. 19.2W (full load working) / 3.4W (idle) power consuming (board input, without fan). here a detail spec table:
Technology: Spartan6 -LX150 -2I (or -3C)
speed (MH/s): 380
$: 569 (1) / 469$ (multiple of 30) (-5$ if you do not need the adapter, recommend for bulk orders, they are heavy)
W: 4.5 for idle / 21 for full load. (notice this is the on wall power, include the adapter losses and fan)