Yes, you can run dual channel kits in LGA1366 motherboards. There will be a decrease in the performance of the memory sub-system though as a result of going with dual-channel rather than triple-channel, and less/slower throughput.
Yes, LGA1366 boards aren't exactly cheap. But they have been going down in price. They're a bit cheaper now than they were 2-3 years ago, I'd say $50-100 less than they were three years ago, on average. With GPU mining now becoming unprofitable with the decrease in bitcoin values the prices of hardware should go down more in the future (I think LGA1366 was a popular platform for this, IIRC). Plus there's also the decrease in CPU-folding (which LGA1366 was popular for with their hexa-core processors).
There are plenty of LGA1366 motherboards coming on the market as-of-late due to their owners' upgrading to newer platforms such as LGA1150, LGA2011, and LGA2011-3. So, there is a chance of finding good deals, since they can't all sell for really high prices (or have multiple bidders engaging in bidding wars to buy them). On the bright side Quad-core CPU's without hyper-threading are really cheap ($10-30 usually from what I've seen) and Quad-core CPU's with hyper threading are still pretty cheap ($20-60 usually). Quad cores on LGA1366 have come down a lot over the last couple of years, what costs $20-60 now were $60-120+ two to three years ago.
