Thanks eric and meerzistar for the replies, very informative. Eric, I will try your 2' test and see how the highs sound. Thinking about it, the speaker placement could be a big part of the issue, but it being my living room puts a damper on moving them out from the wall much more than is currently the case.
A short while ago I did happen to remove one of what Scan Speak refers to as a "mid woofer" from my speakers. I was pleased to note that Madison Sound carries the exact 7" replacement model/part number.
If Scan Speak sells the exact model/part number for the tweeter, is it a safe bet to replace them without worrying about anything? Note that I do think that installing poly caps for the tweeters is probably the big part of what is needed.
Thanks,
George