why should i buy a expensive motherboard, how does it differ from a cheap one. thanks
Not all the time what is expensive is better than something with lower price.
You don't have to buy expensive mobo, a cheaper mobo can have all what you need, on an expensive mobo there is features what you will never use. Like 3or 4 PCIE X16.
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It all depends on your intended use, components, and requirements. Example it makes no sense to purchase a $300+ MOBO with a non-overclock CPU and using the iGPU ports with one HDD and a DVD with 2x2GB of RAM. However, it does make sense if using 2, 3 or 4 GPU's with a CPU that can be overclocked with 4x4GB RAM.