Hello Neil and welcome to the Cow Audio Forum.
In addition to the advice given to date, here are a few additional thoughts.
In the “old days”, surround mixing systems used satellite speakers for the dialogue, side and rear speakers. They didn’t have to be as good as the L/R because most consumers home systems were not that spectacular.
As home theater systems evolved, the trend to having speakers equal to the front L/R speakers have required studios to up their game as well.
About composers and mixing. There are thousands of composers who submit their mixes in stereo. Film productions seldom do anything severe with the music that require surround mixing. If they do, then tracks or submixes can be used.
Composers may or may not use a sub. More has to do with the individual setup and how capable their main L/R are in reproducing the lows. The Klein and Hummel 0110 are great small monitors but they require a sub, the K&H 0300 have a pretty solid low end and don’t in most cases. I don’t know about the yamaha speakers mentioned. I haven’t seen much about them and haven’t heard them. Genelec has an excellent reputation and I like the Event Opals. I use legacy JBL L100 on one of my workstations.
To be sure, composers working on techno and some dance music absolutely require subs because their music is reproduced in clubs with “big bottom” systems.
Do you have the right space in which to deploy surround monitors? That’s a big question. If the architecture is not conducive, your results will be limited.
Regards,
Ty

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