Mayhaps I can shed some light on this subject. L1090's will go easily for +/- $500 depending on condition. They are absolutely marvelous speakers, but they are rare these days. I took a very long sebatical from the ADS game on the order of some 12 years, the last pair I had were 1290's in medium oak finish. My 1090's came up in a trade deal and I could not resist. To make a long story short I had a couple of amps floating around and made an even swap.
Although I do not run them stock, but instead run them capacitor shunted HF-UHF and actively crossed over as a 2-way setup, the factory crossovers at 24dB/octave are very nice. My pair are in black. Yes, the doping compound on the domes is very sticky and will collect dust, cat/dog hair, and anything else in the vecinity of them, but should not affect the sound. These are very inefficent speakers and the drivers are very hard to come by. If you haven't removed the plastic cover from that driver yet, I suggest you do so. They were for shipping only and were supposed to be removed at set-up time.
Also, The drivers were manufactured in Germany by Braun, and Cantons use the same drivers, so ADS and Canton are essentially the same with some slight differences in crossover and cabinet design.
Also, beware they are too inefficient for single ended triodes unless you keep it WAY DOWN. The speakers are AMAZING to the point where I dug out a pair of Perreaux 2150's to drive them. A funny thing about the ADS L-Series is they are way inefficent, and they can't handle alot of power. You have a ballpark figure or a "Happy Window". Give them too much power and they self-destruct. Give them too little power and they will sound stifled and possibly be destroyed from a badly behaving amplifier and out-of-bandwidth secondary harmonics.
My strongest recommendation I can give is be gentle with them. They are very fragile and replacement drivers are about as easy to find as hens' teeth.
Hope this helps...
-A