Resistance of the individual channels is hardly a good measure of matching since that resistance is simply used as a voltage divider so the two wipers could be wildly different and still well matched. A better way to check and see if it's in the pot is to feed the amp a 1kHz wave and measure v-in and v-out at the pot. You can use your laptop as a signal generator for this purpose and get much better and easily interpreted results. And lest anyone think I was smart enough to come up with this on my own, Justin is the one who suggested it to me when I was fighting a similar problem on a different amp.