Different kinds of product: one is active with its amplifier built in, the other passive and needs one. Judge them on how you want to own the system, not just the specs.
| Area | Better | Why |
|---|
| Bass | B | Klipsch RP-600M digs deeper - 45Hz against 50Hz. A subwoofer would even that out. |
| What you buy | depends | Klipsch The Fives II is a complete system - just add a source. Klipsch RP-600M also needs an amplifier: more money and another box, but you choose it. |
| Connections | depends | Klipsch The Fives II has Bluetooth, HDMI and phono built in. With Klipsch RP-600M that all comes from the amplifier you pair it with. |
| Upgrade path | depends | Klipsch RP-600M can be re-amped later and outlive several amplifiers; Klipsch The Fives II ages as one unit. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | depends | Klipsch The Fives II: a sub output; Klipsch RP-600M: bi-amping. |
| Price | B | Klipsch RP-600M is cheaper - $459 against $1,399, about 67% less; arguably a different class. Speakers only - an amplifier narrows that gap. |
A Klipsch The Fives II B Klipsch RP-600M
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?
Klipsch The Fives II suits you if you want one box, ready to play, with nothing else to buy. Klipsch RP-600M suits you if you already have an amplifier, want to choose the electronics, or expect to upgrade in stages. Neither is the better speaker in the abstract. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 50Hz anyway, so judge these on the other rows instead. Think about the whole system, not just the speakers: the roughly $940 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
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.