Honestly, price is too much. I bought a 2005 5.9 SL on sale for $3000 back in 2006. (same frame, but with Dura-Ace); and it was from my LBS. Love the bike, was worth more than I paid.
But $2100 for a 6-year-old bike with *6600* Ultegra? I'd look elsewhere, unless you get them to throw in some...