baclagg, I used to own a pair of Decade D2’s that I bought from Ty used and sold them a couple of years ago so while the market is smaller for the Tylers they can be sold used, but you will defiantly take a hit if you buy them new and decide to sell (true of any speaker really but bigger loss with the Tylers). The bigger the physical size the tougher the sell, again pretty true of any speaker. I talked to Ty about the Highlands several years ago and he said they were very similar to the Decade’s but a little better of everything, better detail retrieval, bass extension, sound stage, imaging, etc.
For a comparison I found the Decade’s, though very large speakers, to have a very linear, monitor like approach to the sound. Top to bottom linear sound. Sort of a what goes in is what comes out sort of speakers. Imaging was very good but smaller speakers did do it better. They aren’t going to accentuate any part of the frequency band for an acoustic "bump" or pleasing side effect to the sound signature unless the room added it. The D2’s had good bass response but nothing that made me exclaim wow like I’ve done recently with some much smaller and much less expensive speakers that probably do rely on some sort of designed-in effect.
That all being said I would still love to find a pair of used Highlands partly because of the quality of drivers used in the speakers and Danny Richie’s involvement with much of the Tyler line. Good quality drivers with good behavior don’t require complex crossover with a huge parts count. That and I have never owned beryllium tweeters and would love to give them a shot even though I’ve been in the soft dome and ring radiator tweeter camp for a while.
Best of luck.