So, i'm searching for a good x99 motherboard which do you recommend?
Some of the motherboards that I have found
MSI X99A SLI Plus
Gigabyte GA-X99-UD4
MSI X99A RAIDER
Asus X99-A/USB 3.1
ASRock X99M Extreme4
Gigabyte GA-X99-SLI
I like the ASRock Extreme 4. It is very well reviewed and very inexpensive (relatively speaking) but has all the bits you need. Here's a review. In the USA, at least, the price-performance of that board is excellent.