As the subject states, I've owned a pair of walnut SDA-1Cs since new, serial # 11XXX. I believe they have the SL2000 tweeter but if I recall correctly subsequent polk speaker models came with an upgraded tweeter (SL2500 ???).
I understand there is an upgraded tweeter available. Is this a worthwhile upgrade from a cost/performance perspective? I'd also appreciate any other links or information on the entire, late great SDA line.