The Polk vintage forum discusses, among a number of topics, mods numerous and particular to the SDA series. Review of the vintage forum shows the SDA series being held as the most respected speaker effort by Polk Audio.
My own walk in this landscape over the past eight years includes transforming my pair of studio SDA 1Cs by: replacing the SL2000 tweeters referenced by richidoo (they were definitely shrill in areas) for the newer silk-dome RDO-194 tweets plus diffractionbegone Tweeter Felt Surrounds, having the XOs rebuilt with upgraded components, applying Walker SST on all the internal and external connections, and some other mods (including a custom version of Polk's AI-1 isolation transformer that allows some SDA models to be used with non-common ground amplifiers). My speakers as currently are
quite a different beast than the stock speakers I purchased in 1989, and if one has the opportunity, I recommend giving an upgraded pair a listen.
I couldn't say nervosa is over at the Polk vintage forum. Rather, nervosa appears most visible vis a vis sharing / learning about / applying myriad mods to the SDA series, the results of which seem to keep the forum members happy and deferring new speaker purchases. My personal experience disclosed a substantive return on various mod investments - for example, the tweeter replacement and XO redo (XOs were quite rea$onably rebuilt by one of the Polk forum members, which reminds me of how invaluable and heartwarming various audio forums and forum members can be) and had me wishing I'd done those mods years ago. I'd be remiss by not reporting my nervosa in changing out related amps and source components during that period, plus having dedicated 20A circuits installed, too.
Regarding the Monitor 60s, I think they might work for someone who wants a starter system or would like to get something initially going related to home theater.
