With DaVinci Resolve, it is paramount to have a strong GPU. You will notice quite a large difference in that program if you upgrade your GPU to something competent, like the GTX 1060. This is a very good website that outlines part decisions in regards to editing/encoding http://www.logicalincrements.com/articles/videoediting. I had to use prices from Germany, since pcpartpicker doesn't have an option for Finland, so apologies if there are some inaccuracies in pricing. Here is what I recommend:
PCPartPicker part list:
https://de.pcpartpicker.com/list/49mPJ8
Price breakdown by merchant: https://de.pcpartpicker.com/list/49mPJ8/by_merchant/
CPU: Intel - Core i7-8700K 3.7GHz 6-Core Processor (€332.94 @ Mindfactory)
CPU Cooler: CRYORIG - H7 49.0 CFM CPU Cooler (€31.99 @ Aquatuning)
Motherboard: MSI - Z370-A PRO ATX LGA1151 Motherboard (€104.84 @ Mindfactory)
Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3200 Memory (€168.89 @ Alternate)
Storage: Samsung - 860 Evo 500GB 2.5" Solid State Drive (€114.51 @ Amazon Deutschland)
Video Card: EVGA - GeForce GTX 1060 6GB 6GB GAMING Video Card (€299.90 @ Caseking)
Case: Fractal Design - Meshify C Dark TG ATX Mid Tower Case (€76.20 @ Amazon Deutschland)
Power Supply: SeaSonic - FOCUS Plus Platinum 650W 80+ Platinum Certified Fully-Modular ATX Power Supply (€110.06 @ Amazon Deutschland)
Total: €1239.33
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-06-04 20:32 CEST+0200
You could save money if you selected to go for a non K variant of the 8700, however, doing so would lower your clock speeds, something that editors/encoders love. Also, I splurged a bit on the PSU, given I HIGHLY recommend you spend more money on a QUALITY PSU, and SeaSonic is one of the best brands you can get. If I need to shift prices around, just let me know. As far as the RAM is concerned, you may end up needing more than 16 GB, I am unsure of your project settings/other use cases. Again, I can work that into the budget if need be.
As far as an increase in performance is concerned, there will be a MASSIVE improvement. The HQ suffers indefinitely when compared to the behemoth that is the 8700K
http://cpu.userbenchmark.com/Compare/Intel-Core-i7-8700K-vs-Intel-Core-i7-4720HQ/3937vsm20045 , and the same goes for the 1060 vs a mobile 960M.