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 | A | Polk R700 digs deeper - 38Hz against 70Hz. |
| Amplifier needs | A | Polk R700 is more sensitive (88dB vs 86dB), so it goes louder on the same amplifier. |
| Size | depends | Polk Audio Reserve R900 is easier to place; Polk R700 is bigger, which usually goes with fuller bass. Your room decides. |
| Type | depends | A Passive Floor-standing against a Passive Surround - a different job rather than a better one. |
| Expandability | A | Polk R700: bi-amping. |
| Price | B | Polk Audio Reserve R900 is cheaper - $599 against $2,198, about 73% less; arguably a different class. |
A Polk R700 B Polk Audio Reserve R900
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?
The usual trade-off: Polk R700 measures better, Polk Audio Reserve R900 costs about about 3.7x the price% less. Whether that gap is worth the money is the call only you can make - and in a normal room it is often smaller than the numbers suggest. 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 R700 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.