I am not so sure about the motherboard now if you are going the GPU way, this was only for CPU setup.
MSI as bought by @jodyls27 has one big issue , it takes 2.5 pcie slot space due to its more than dual width.
My Sapphire r9 390 takes only 2 slots. So I have a chance to fit another one in the same cabinet.
Temp. till now for Saphire Trix are great, 33 at idle, when rendering or playing game 55 C, when benchmarking with uni heaven extreme goes up to 65 degrees.
This is also because of all the fans and cooling items Dennis suggested above. So go through this thread properly.
You do not need a processor cooling fan if you are using cooler master cpu cooler. Instead of double fan cpu cooler you can use Cooler Master seidon 120v+ like mine. It will save you money and space. Those extra slots can be used by normal cooler master sickle flow fans for exhaust.
You can also use a 250 GB solid state drive if it saves you money.
The most important item missing is a PSU and I am realizing it after buying the sapphire.
I am getting beeps from my UPS when rendering or running uni-heaven, so I had to connect the CPU directly to the power socket on wall. Need to buy another High end UPS which can support 2 Saphire in future.
Also the power usage is directly affecting my renders. As I mentioned above I am having issues with GPU above and opened a thread ( which Dennis closed which in his defence was right thing to do) .
First I was getting the Artefacts white in color like this randomly, sometimes render worked well, sometimes they were horrible. I have worked on this issue whole day today and used after burner to increase the power limit of the GPU to max. Now the artefacts are gone and it is rendering fine..
My problems with AMD GPU are two fold: one is this GPU power limit above, other is the GPU is magnifying small compositing or node errors, wrong node setup as it doesn't support transparent shadows yet officially. I am using the experimental build. CPU completely ignores these small artifacts which the GPU is rendering in a magnified version.
I am still working on these and they look like they can be fixed by compositing and working on the materials. This is happening because I was working with CPU from the start and now suddenly changing to GPU is causing all this.
If you work in GPU from scratch you will probably solve these problems and then move ahead.
So save money to buy a good PSU, if you are going to use 2 GPU later, invest in a 1200 W PSU. You will obviously need a compatible Motherboard for that as well.
Meanwhile in 2 months, they will probably release a better version of Blender for AMD GPUs and I am also testing and working with this AMD GPU to write down a good workflow. There are issues but they can be sorted out.
Also Dennis and others can help you better, because I learned from them.