Which Harbeth?

7's and 5's...3's if you listen near field.

I have the same size room with C7ES3's and they're perfect for my room. I wouldn't go any smaller unless as Chashas1 said, you listen nearfield.

Don't buy Harbeths w/o listening to them (i.e., just based on their reputation). (Unless you buy them used and can resell them w/o much of a loss or if $$ is not an issue. They do resell quite easily.) Harbeths have a unique sound signature. Lot's of people love it. Some find it lacking in resolution, which is what I think is a necessary factor in high end sound.

Definitely listen first if at all possible with music and equipment your are familiar with. Makes a load of difference and will keep you from buyers remorse.

Personally I prefer speakers that are more dynamic, fast and with greater resolution. As always your ears and budget will decide.

Funny responses... The op asks which models, and you guys are trying to get him to get other brands.... Hilarious!
Perhaps like many he loves Harbeths? And maybe wouldn't like your etched, audiophile, showy type of speakers? If indeed you had those kinds...