It depends on what your expectations are and what you are comparing it to. The Arc will sound great in your room especially when playing 5.1 and Dolby Atmos audio. And compared to the TV’s internal speakers, the Arc will give you a pretty noticeable improvement.

Will the Arc sound better with a Sub? Of course. But many users are very content with just the Arc alone and the amount of bass it produces.

We use a Beam without a Sub in a 3x3 meter bedroom, mostly watching TV shows and it is more than adequate.

Haven’t really tried our Arc with the Sub turned off in our larger living space, it was a replacement for a Beam and that already had the Sub in place. Still I’m sure it would be a big step up from the Beam, even more from the TV speakers. Adding the Sub, mostly for music and a few movies was a nice improvement.

We aren’t tempted to drop back to a Sub-mini or step up to a second Sub there.

Same for the bedroom, even with the less capable Beam.