Awhile ago after JUST "reacquiring" my DT880s, I went out and decided to buy some 650s which I had been lusting for over the past couple days. Luckily, I managed to work my way out of them, and I do think I've ever felt more content with my decision. Getting the money ready and then declining made me feel incredibly good for some reason, and now -- although I still want a pair one day... -- I'm not ready to pounce on them again right away.
My DT880s just got to me today after waiting three weeks for an airmail shipment. Those were some hard weeks, but it was unquestionably worth every minute of waiting. I can't speak highly enough of these phones. Lucky for me, Sony and Sennheiser have already scared me away with the SA3000s and HD280s. I know those don't speak at all for the quality of the higher end phones from them, but it's a good reason for me to stay away from buying more. And as far as I was concerned, the SA3000s sounded prettu bad even with the Black Dragon cable upgrade, so I'll be staying away from those too unless it's for functional value.
So my suggestion to you: Buy them tonight and cancel the order in the morning if you feel really guilty. Otherwise, they're an awesome set of phones to have. I'll be more happy with them for quite some time to come.