Short answer: the Polk Monitor XT20. It ranks #157 of 222 bookshelf speakers by sound quality, rated 3.4/5, at $277.50; the GR-Research Klipsch RP-600M Upgrade ranks #179, rated 3.2/5, and costs $279, so there is little reason to consider the other one.
What the Polk Monitor XT20 does well: Budget bookshelf speakers with good bass for their size and a fairly wide soundstage. The catch: Notably bright treble, elevated roughly 1-5dB above the midrange depending on frequency: a characteristic shared across the whole Polk XT lineup, requiring either EQ or toe-out to tame.
The case for the GR-Research Klipsch RP-600M Upgrade: A DIY crossover kit that fixes the main flaw of a popular Klipsch bookshelf speaker, with smoother sound and all new parts. The tradeoff: This is a DIY kit, not a finished speaker: you need a pair of the original Klipsch RP-600M, which is discontinued, and must rebuild both crossovers yourself.
Buy the Polk Monitor XT20. It is rated higher for sound quality than the GR-Research Klipsch RP-600M Upgrade and costs less, so only choose the other one for a particular feature it does better.
Still deciding? The full Passive Home rankings cover every ranked option.
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Specifications Side By Side
| Polk Monitor XT20 | GR-Research Klipsch RP-600M Upgrade | |
|---|---|---|
| Price | $277.50 per pair | $279 per pair |
| Ranked | #157 of 222 in Large Size Bookshelf Speakers | #179 of 222 in Large Size Bookshelf Speakers |
| Bass Extension (-10dB) | 43.4Hz (derived, log-interpolated between spinorama.org -9dB/-12dB points) | 40.0Hz (measured, spinorama.org ASR data) |
| Bass Extension (-3dB) | 64.5Hz (measured, Erin’s Audio Corner) | 68.8Hz (measured, spinorama.org ASR data) |
| Dimensions | 13”H x 7.5”W x 11”D (330.2 x 190.5 x 279.4 mm) | 15.7”H x 8”W x 11.9”D (398.8 x 203.2 x 302.3 mm) |
| Impedance | 8 ohms nominal (measured, Erin’s Audio Corner) | - |
| Sensitivity | 86dB (measured by Erin’s Audio Corner; 87dB manufacturer specified) | 86.7dB (measured, Audio Science Review) |
| Drivers | 6.5” bilaminate paper cone woofer, 1” Terylene dome tweeter | 6.5” Cerametallic cone woofer, 1” titanium LTS vented tweeter with Tractrix horn (stock Klipsch RP-600M drivers) |
| Weight | 11.9 lbs (5.4 kg) each | 16.1 lbs (7.3 kg) each |
| Woofer Cabinet | ported | ported |
| Spinorama Preference Score | 4.71 | 5.11 |
| Spinorama Preference Score with Perfect Sub | 7.07 | 7.06 |
| DIY Kit | No | Yes |
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