configure amp 4 or 8 ohm to drive 6 ohm speakers

Hi all, my push-pull vacuum tube power amp can be configured for 4 or 8 ohm load but is currently wired for 8 ohm. The spec on my speakers is 6 ohm. Should I switch the amp to 4 ohm, and if so why? Would it be for sonic reasons or to be safer for the amp? If better to switch, I need to get the info from Cary to change the transformer connections.

amp is Audio Electronic Supply AE-25 super amp with 6l6gc in triode mode.

speakers are Opera Platea's

thanks in advance for any input
Phil