NoBOOBsForNOOBs :
Actually in my country 1700X is around 475 usd dollars and the i7-7700K is 430 usd and the MBs prices are quite the same for the brands so i am really confused what to choose so any advises are welcome.
Like I said it really comes down to what games you play.
Tom's still crowns the 7700k as the best gaming CPU, but thats just in general. Let's say you playing Battlefield 1 a lot, the 1700x would actually cream the 7700k in that game, but in the majority of games the 7700k wins. For the most part, not always mind you, but Core speed is much more beneficial than core count.
As far as motherboards go I really like Asus ROG boards, very easy to OC and generally have the best BIOS to OC, as well as the BIOS being extremely easy to navigate and such. But there are plenty of good ones out there. If you were going to get a high end K-series 7th gen, you're going to want a Z270 MB. The Asus ROG Maximus IX Hero (and Hero Alpha) are widely regarded as one of the best MB's you can get. I have the Maximus VIII (6th gen Intel, Z170) Formula and it's awesome, also has great lighting.
It's all about what features you want though.
Would definitely get a better RAM kit. I'm guessing you have DDR3. With the new MB you'll want DDR4 and at least 8GB. 2133MHz C15 is the typical clock rate and latency, which is perfectly fine, but because of latency factors, the fastest you can get (if you want it, it is also really negligible) is 3466MHz C16, or 3000MHz C15, in that order. Other than that its all blowing smoke and matters little for gaming.