Hi there. I own the AsRock 870 Extreme 3 Motherboard myself and can offer a little insight on some issues I ran into with the G.Skill memory. I didn't use either one of the memories you listed but I did use this (Newegg.com - G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-4GBRL). It's also a G.Skill product that wasn't on their QVL list. To be honest I had NOTHING but issues with this G.Skill ram and this motherboard. The ram passed many many hours of memtest86 yet I still had random bluescreens from day one of building my new computer. Naturally since the ram passed I assumed it had to be something else and lets just say a couple windows installs later, hardware swaps and probably a 100 hours wasted on researching the issue only to realize it was the ram all along. I switched to some Corsair memory (Newegg.com - CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMZ8GX3M2A1600C9) and haven't had one single issue since.
For whatever reason the AsRock board at least in my case seems to HATE G.Skill ram, or the ram hates it not sure what yet :P. If you do decide to try what you have my only advice is make sure ALL the timings are properly detected in bios, not just the main 4 timings. I noticed with everything set on auto the board was using timings 1-2 different than what they should be on a couple other timings. Once I did that the issue got a lot less worse with the G.Skill ram but I still had blue screens upon cold boot with that ram. I guess it's possible the ram was still defective even though it could seriously run for 24 hours passing memtest flawlessly but I don't know! I just mailed the ram back to them to see what they say two days ago.
Sorry for the long post I figured I'd offer my experience with similar ram and this motherboard. While researching I did find many other posts especially on G.Skill forums with issues with this board and their ram so just an FYI. Best of luck on your build! Oh and one last thing, make sure any 1600 DDR3 ram you install is installed in the two blue slots (further away from the cpu) as per motherboard manual recommendation.