Tony: I will reply with what I believe to be true based on my own research, and await correction or additional information from other, possibly more knowledgable individuals:
20,000 FA-made for U.S. market. (6-1 gear ratio) Comes with large capacity spool. (No spare). U.S. warranty.
10,000--lower (4.5/1? gear ratio) FA-same as above, but with lower capacity spool. Some say this is an advantage in casting, not necessarily because of the capacity, but possibly because of the shape of the spool lip. Others, seemingly knowledgable as well, dispute that. I have wondered if there might be a difference, not only in spool capacity but in spool diameter, but I have no knowledge of that.
20,000/10,000 SW-made for the Japanese market but available through a limited number of U.S. dealers. (I bought mine as well as my 8,000WS, from Anglers Pro Shop) Appears to be identical to the FA model. Comes with spare spool and two handles for roughly the same price as the U.S. models. (I cannot speak about Ebay because I do not use them.) The spare spool on this model is marked "Stella 16,000" and has smaller capacity than the regular spool, and is, I think, closer to the 10,000 in capacity.
Speculation on several boards is that new ones are coming out soon--first for the Japanese markets, with a delay of usually a few months at least before they hit the U.S.
I own the 20,000 SW, and it is my understanding from the dealer from whom I purchased it (Randy at Anglers Pro Shop) that the parts are interchangeable with FA parts. So even though I can't/won't send it back to Japan for servicing, I am betting I won't wear it out or break it prior to the end of warranty, at which time, I can have it worked on for a fee, here.
there is also a 20000PG version, which I have. I bought it from Japan, and the pg is for power gear. i have to reel very fast to keep up with the sw or fa. it is great once they are hooked, but you really have to work the reel to get some good action topwaters. it works and has caught 7 yft on three trips, with one trip only getting a bft. not bad! i like 'em both, the reels are so damn smooth. amazingly smooth, imo.
j2hunt: They really are smooth. I bought a Stella 6-1 20,000 when they first came out, but when I tried a Stella, I had to have one of those as well, even though I really didnt "need" one at the time. In fact I ended up buying almost the whole line from 20K to 1K.
Someone who did their homework pointed out to me that the current price on Randy's site is substantially more than "the same price" as the FA in the U.S. I don't remember exactly what I paid, but I have to correct my remarks in that regard. But the price of the whole package was substantially less than I would have paid for the FA, spool, and handle, and my greed for a spare spool outweighed my desire for the warranty, especially in view of the fact that I knew it would get very little use during the warranty period.