Rome,
One additional thought - if your single speaker is able to be biwired - that is, has separate sets of connectors for low-frequency and high-frequency ranges, you should actually be able to connect both "channels" of your receiver while in mono mode. Remove the speaker's jumpers and then conventionally connect "left channel" outputs to one set of terminals and then "right channel" outputs to the other. Both channels would actually be outputting in mono mode. Not sure whether this will actually deliver more power or better dynamics but it may be worth a try.
Best,
One additional thought - if your single speaker is able to be biwired - that is, has separate sets of connectors for low-frequency and high-frequency ranges, you should actually be able to connect both "channels" of your receiver while in mono mode. Remove the speaker's jumpers and then conventionally connect "left channel" outputs to one set of terminals and then "right channel" outputs to the other. Both channels would actually be outputting in mono mode. Not sure whether this will actually deliver more power or better dynamics but it may be worth a try.
Best,