[old_tv_nut]

If your amp can handle 6 ohms minimum, then you need to put an additional resistor in series with the output before connecting the L-pad and 6 ohm speakers. The minimum resistance load will be with the L-pad set to max, which will be 8 ohms (pad) in parallel with 6 ohms (speaker) = 3.4 ohms. A series 3 ohm 50 watt would do. This also means you would have a minimum attenuation of about 6 dB when the L=pad is set to max, but from your description, you need it.