folks. just got quite old Westlake BBSM8 which takes over Tannoy Stirling TW as main sp, relocate Stirling to back surr sp. now problem occurs, don't know how to setup IMPEDANCE? Stirling is 8 ohms norm / 5.5 ohms min, but BBSM8 is 4 ohms norm / 2 ohms min. there is no crossover ohms. so which IMPEDANCE should I choose on amp, Onkyo NR900, 6 or 4 ohms? any damage to sp/amp? BTW, anyone has BBSM8 spec? also consider to get muRata ES105 super tweeter (8 ohms). BBSM8 has hi/lo inputs, so I should connect from NR900 to BBSM8 lo, bi-wire to hi, then link to ES105? is this correct? tks for your help.