If it's too good to be true....

I wholeheartedly agree with all of the previous advice.

However, as a first screen, you may want to take a look at the actual feedback of the seller and not just rely on the absolute number. In several cases, fraudulent sellers seem to have assumed dormant seller accounts, salted them with one or two recent feedbacks, and then listed various high ticket items (audio equipment, plasma TV's, PCs) at too good to be true prices.

If you are looking at the "New" Creek gear, this screen would say do some more due diligence on the seller.

I usually ascribe to the adage, "If it's too good to be true, it probably is," but, sometimes, I've looked at stuff that seemed too good to be true -- but it WAS true! I have purchased items up to $1000 less than the going rate USED.
Certainly, you must know your seller. A phone call usually helps develop confidence.
On the other hand, I've also had questions about buyers. Recently, I was about to accept a credit card payment from a buyer in Indonesia when I saw a reference to credit cards on another audiogoner's sale listing as not being acceptable. When I contacted him, he told me there are scams with credit cards from Indonesia. I asked the "buyer" to wire the money -- and never heard from him again.

Check feedback and reassure yourself with contact about the seller. If something still feels funny then - trust the feeling and walk away.

That having been said, you can usually get brand new stuff for 15-20% off MSRP new in store and 20-30% off if you find the right source, so look at the $600 off and figure if the % is actually high. Almost nobody goes over about 30% new unless there is a reason (no dealer in West coast for example, the company may sell direct at substantial discount).

Good luck,
Jacob