Whether they're 20's or 20i's (bi-wirable), you can isolate the woofers by removing the mid/tweeter fuse.
1. Play the offending music with those fuses out and if you hear the same scratchiness, it's likely that the woofers are your problem.
2. To be sure - REVERSE: Remove the Woofer fuses and replace the tweeter/mid fuses. If you hear the same scratchiness coming from the mids, it's likely your problem is NOT the speakers but somewhere else.
3. If it appears to be only the woofers, remove the grills and have a look at the foam surrounds. If they are torn, you can replace them yourself fairly easily. It's about a 4 hour job start to finish. IMO Regnar's prices (and their attitude) is total ripoff. If you want someone else to do it, pull the woofers and send them to MillerSound (215-412-7700):
4. My guess is it's the woofer surrounds, because at their age, they're definitely overdue (atmospheric ozone breaks them down) - but the odd thing is that they both went simultaneously. Possible but unusual, unless you went from chamber music to '70's disco at high volume.
5. IMO, the DQ's are worth saving - once you're used to the sweet DQ midrange and imaging it's hard to find anything that's as nice in the recent crop of speakers. Either that or find a pair of DQ-20i's on Ebay so you can biwire. A friend of mine just bought a pair a couple of days ago:
Hope this helps - if you need advice about doing a refoaming yourself, email me. I've done a number of them and can direct you to the source for PROPER surrounds - there are some being sold on Ebay that aren't good.