It’s not as much how big or small the sweet spot is on D300.
Basically it’s about speaker positioning and how much space/room you have to play with it.
But there is cost for more wider spot.
If you use positions like these. You basically have bit wider and bit more narrow sweet spots.
Will it be enough for sofa? Testing will tell.
In my 3 seat sofa with my speakers there really is only 1 sweet spot with speakers pointing at the center position. It is the Center seat but it kinda covers a 55" TV @ 3m / 10ft distance so you can move bit and sweet spot remains “in the frame of TV”.
Left seat has the spot about in between the left speaker and TV
Right seat has the sport about in between the right speaker and TV.