Siblings in Klipsch's Reference Premiere (RP) II series, so they share a family sound. It comes down to size, output and price.
| Area | Better | Why |
|---|
| Bass | B | Klipsch RP-500M II digs deeper - 50Hz against 58Hz. A subwoofer would even that out. |
| Amplifier needs | evenly matched | Similar sensitivity (93dB vs 92dB) - both want much the same power. |
| Size | depends | Klipsch Reference Premiere RP 500SA II is easier to place; Klipsch RP-500M II is bigger, which usually goes with fuller bass. Your room decides. |
| Type | depends | A Passive Surround against a Passive Bookshelf - a different job rather than a better one. |
| Price | A | Klipsch Reference Premiere RP 500SA II is cheaper - $450 against $599, about 25% less. |
A Klipsch Reference Premiere RP 500SA II B Klipsch RP-500M II
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: Klipsch RP-500M II measures better, Klipsch Reference Premiere RP 500SA II costs about about 33% more% 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 58Hz anyway, which makes the cheaper Klipsch Reference Premiere RP 500SA II much easier to justify.
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.