Defiantly not phonos, since they are for low level signals, I know some crap audio systems use them for speakers, but that's really cheap stuff that will be pushing under a watt thru them.
I would go for speakon connectors. They are made for the job and there is no worries about anyone having a problem with them over the whole "Europeans are idiots and stick their banana plugs into the power outlet" issues that plauge UK audio gear with those horrid BFA plugs being the result.