Can I get "Great" used speakers for $1800??

There's a lot of excellent speakers out there at that price range, many of which would go with your listening taste. Might be good to let us know which amp you are using, though. Some examples:
Thiel 3.6, B&W 802 matrix,Tylo Ref Monitors, NHT 3.3, Aerial (6 or 7?), Revel Performa 30, Infinity Prelude PFR.

Consider the following only if you have a high power/high current solid state amp: Magnepan 3.3 or 3.5, Dunlavy 4.
Best of luck.

B&W Nautilus 805, JM Reynaud Trente, Merlim TSM-Milennium.

All of these are bookshelf speakers, but I've had all in my home (Trentes right now). EXCELLENT sound.
All of these are Musical, Accurate, with incredible soundstaging and imaging, and tight bass down to 40hz or so.

I use a Rogue Tempest in triode (30watts) and get great strong bass from my trentes, let me turn it up so you can hear.

I'll second Thiels and Maggies.

New Carolina Audio 6XL's go fo $1800 and are fantastic transmission line loaded 2 ways with series crossovers. Hand made in Charleston www.carolinaaudio.com

I have the JTM's using the Jordan JX92s full range driver and I have never been this blown away by a speaker..... only $1500... I honestly can't think of a speaker at any price that I'd rather have in my living room.

Gershman Acoustics Cameleon, under $1800-, NEW!!! I heard them at both the 2002 and 2003 C.E.S shows, and was floored both times! And at the 2003 show, these speakers were used with a CD player, and integrated amp, with stock power cords, and sounded awesome for a system total cost of around $4500-! Contact me for more info regarding the set-up.