New AVR, Old Speakers
I suspect your DCM speakers will work just fine with the Onkyo TX-NR609 (reviewed here ). They all have a nominal impedance of 8Ω, which the Onkyo can drive with no problem at all. The KX-12 (seen here) can handle up to 250 watts of power, while the KX Center tops out at 125W and the KX-6 can handle up to 100W. The TX-NR809's power output is spec'd at 135W per channel into 8Ωthough it measured somewhat lower than that at 0.1% and 1% distortion with five and seven channels driven continuouslyso the center and surrounds will be fine as long as you don't crank it totally full blast.
If you still want to upgrade, our top picks for a surround speaker package in the $2000 range are the Mordaunt-Short Aviano 1 (reviewed here) and the JBL Control NOW AW (reviewed here). However, these are compact speaker systems, somewhat smaller than your DCM speakers. Unless there's something defective with the DCMs or you don't like their sound, I'd keep 'em.
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