I bought all 6 boards, other bidder resigned.
I fixed boards by flashing them with HashVoodoo bitstream.
My results so far:
4 boards running 827, 835, 840, 840 MH/s (that's because bfgminer limit 210 MHz per chip, I will increase it later with cgminer)
1 board running 622 MH/s - 202MHz, 210 MHz, 210 MHz, OFF (one FPGA chip is dead)
1 board running 620 MH/s - 200MHz, 210 MHz, 210 MHz, OFF (one FPGA chip is dead)
Entropy-uc estimated it as:
Two of the boards kick out 50% hardware errors, resulting in an effective hashrate of ~400 MH/s
3 boards have one pair operating below standard for hash rates ~600 MH/s
1 board was programmed with 170 MH/s bitstreams, so it is running at ~680 MH/s
That's 400+400+600+600+600+680 = ~3280
I already have ~4564 (no less than that).
I am very happy with the results. Thank you again Entropy-uc!