Replacing woofer for Pioneer CS 822a

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I have a pair of Pioneer CS 822a speakers - 8 ohms which has a 13" woofer. I like the mids and highs but the low frequency response is not upto the expectation. The manual says these hit down to 25hz which they actually do, but the do not sound boomy. I also have a pair of Magnat Monitor Supreme 100 which has 2 6.5" woofers and sounds much boomy than this 13" beast. I decided to replace the 13" woofer with a new / more efficient one. The multimeter shows an impedance / resistance of 5.6 for the woofer and 6 for the entire box. Would it work if I replace the woofer with another woofer of 8 ohms ?

Any response / pointers would be highly appreciated.