I don't have any revelations for you on the Synergy series in question except to say they are not current Klipsch technology. Most of what Klipsch is putting out these days all looks the same on the outside: but the under the covers tech does vary quite a bit. Its hard to get a read on these for "age" but the owners manual is Copyright 2010 for the Synergy F300. If the speakers had a 2 year production run that would mean they may have been taken out of the current production status in about 2012, give or take.
The only places you'll see these for sale is on some sort of barn burner sale. Nobody is stocking them and selling them as current technology. Having said all that, is a speaker that could have been sitting in a warehouse new in the box for nearly 10 years worth $299 bucks? I guess it depends on what you have plans for that could also use $299 bucks.
I would suspect they would sound just fine if you like the Klipsch sound and at that price its hard to go wrong.