Siblings in Polk Audio's Reserve series, so they share a family sound. It comes down to size, output and price.
| Area | Better | Why |
|---|
| Bass | B | Polk R500 digs deeper - 49Hz against 70Hz. |
| Amplifier needs | evenly matched | Similar sensitivity (86dB vs 87dB) - both want much the same power. |
| Size | depends | Polk Audio Reserve R900 is easier to place; Polk R500 is bigger, which usually goes with fuller bass. Your room decides. |
| Type | depends | A Passive Surround against a Passive Floor-standing - a different job rather than a better one. |
| Price | A | Polk Audio Reserve R900 is cheaper - $599 against $1,298, about 54% less; arguably a different class. |
A Polk Audio Reserve R900 B Polk R500
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Polk R500 is ahead, but only on 1 of the measured areas, and it costs about 117% more. That is a lot of money for a narrow margin on paper - Polk Audio Reserve R900 looks like the sensible buy unless something else about the Polk R500 appeals to you. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 70Hz anyway, which makes the cheaper Polk Audio Reserve R900 much easier to justify. In a large or open-plan room, Polk R500 has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, Polk Audio Reserve R900 is the easier speaker to get right.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.