First lets clear some confusion, ANY motherboard can handle the jobs you want to do. The speed difference between a $300 motherboard and a $100 motherboard with the same CPU and same GPU is ZERO! Higher end boards offer a lot of neat features but most of them are wasted. Buying a motherboard you need to ask yourself two basic questions.
1) Will I be overclocking? If you are planning to overclocking, spending a little extra money can help as many of the more expensive boards have better overclocking ability. The how much you need to spend however is still not as high as people think. Basic overclocking, that is a limited overclocking without pushing voltages can be done even on very budget minded boards. However even if you want tp push the overclock to higher levels, you can often find great boards at the $150 price point that can keep up with more expensive boards.
2) Are you going to use a multi-card system for the GPU? Again you will find that if you do plan to go with a Crossfire or SLI solution that you do not need to go to expensive boards to get the best results. The key here to me is to look at the various board layouts and see which has the best design to give both cards room to breath. In the AMD CPU arena if you are not going to Crossfire then I suggest looking at 970 based motherboards. They have a great price point, good feature set and only really lose Crossfire over higher cost boards.
I would personally do more research into the software I am using to find how it functions with multi-threading. If you can find something that pushes the cores hard enough the FX 8 core is actually a solid chip. The issue it has faced in the enthusiast and consumer market is that so little really pushes the design and the areas were the design excels is not shown. Also depending on the level of work you will be doing you might want to consider and Intel Extreme solution. Quad channel memory suffers from much the same frustration that the AMD FX does in the fact that nothing in the current computing world, with specific exceptions, push the memory bandwidth and thus allows it to show off.
