I believe my first GPU purchases for mining were of HD6870s. They weren't the best miners out, but their 5850 counterparts were impossible to find anywhere. That was the first thing that struck me about Bitcoin when I first learned of it... I found it amazing that it created such demand for GPUs, even before anyone had heard of it, that you couldn't find a single 5800 series GPU anywhere. I eventually fell into the Butterfly Labs trap myself, losing close to 500 BTC in the process, but as with you I had gained a great deal of knowledge. Fast forward another couple of years and this whole Bitcoin fad became the thing I spent most of my time working on (working for is probably a better description).