I have the HS8s and they do sound great, however....
The general consensus is you don't need a subwoofer with 8 inch speakers.
I'm not so sure, there seems a general lack of bass to me. Certainly when compared to music and sound from my tv surround system. I will probably get a subwoofer at some point to improve the sound a bit.
I have Beyerdynamic DT Pro 770 headphones - everyone raves about them, yet my bluetooth Marshall Major IV sound far better in my experience: clearer and more bass: more exciting and clearer vocals with regular music. Obviously I can't use bluetooth headphones during music making and I tend to only use the Marshalls for listening afterwards (even though there is a cable connection). It is at THAT point in my music making process I enjoy what I've recorded the absolute best: listening through the Marshalls. So the expensive Yamaha speakers or supposed high quality headphones are not even the best audio experience for me.
If the Marshalls would break, it would be the first thing I would replace. I can't say the same thing about the Yamaha speakers or Beyerdynamic headphones.
Point I'm making is whatever you read or hear or what is supposed to be objectively the best or better, is not necessarily how you are going to perceive sound yourself at all.
The Genos speakers seem very convenient. If Yamaha throws them in when you buy the keyboard, why say no?
