Stuck in a dilemma; please help

According to this thread:

http://www.tomshardware.com/answers/id-2715787/sick-recently-improving.html

I'm stuck between a rock and a hard place. I have not reserved my Windows 10 upgrade yet because I don't know what to do. My Internet keeps randomly disconnecting and does so even after reinstalling the Ethernet drivers and Windows 10 preview. I swapped the Ethernet cable and will go to my ISP office tomorrow to swap the modem. If the issue still persists, but connection is stable on a wireless network USB card, then the Ethernet connection on the motherboard is bad. I will then buy a new motherboard, upgrade my Windows 8.1 to Windows 10, and buy Windows 7 and a new SSD for dual-boot. However, if the modem swap fixes the issue, then I'm still stuck with a decision to either upgrade the motherboard anyway and dual-boot Windows 7 and Windows 10 or keep the existing motherboard and buy Windows 10 and dual-boot it with Windows 8.1. From what I read, ASUS has a better reliability track record than ASRock and has better BIOS options. You can see my specs in my signature. The ASRock Z97M Pro4 just does not look right when paired with an i7-4790k and a full ATX tower. Also I will like to have SLI support should I need to SLI my GPU. So should I just bite the bullet and upgrade the motherboard? I want to get the ASUS Sabertooth Z97 MARK S motherboard for best reliability and warranty. And please do not suggest the ASUS Maximus VII HERO or Formula since I do not want a black / red motherboard in a white / blue themed build. Also, I will get a Samsung 850 Pro Series SSD for Windows 10 and use the old SSD for the older OS.
 
I'll see if I could fix the Internet first. If the motherboard is indeed going bad, then I will definitely replace that. I called Time Warner and they saw no issues with the service. So yeah, there is a hardware or equipment issue. But even if the Internet is fixed, I just can't help but to think that I could use that Sabertooth motherboard in my rig. It looks so tempting right now.
 
Well, I spoke with a tech guy at Fry's Electronics and he told me that upgrading the motherboard is not really worth it. Only a handful of games have decent SLI support and the only reason to upgrade is if the motherboard overheats, which is unlikely in a full-tower ATX case. I got a replacement modem, so if the issue is fixed, then I'll keep my existing components and upgrade Windows 8.1 to Windows 10. As for dual-boot, I'll see if I could find a seller on eBay who is selling Windows 7 retail version for a reasonable price.

UPDATE: I replaced the modem; however the network is STILL occurring. I'm going with the wireless connection for the remainder of the week. If connection is stable, then I will order the new motherboard on Monday.

UPDATE: The wireless connection was lost on the PC as well, but my tablet was still connected. I will perform complete virus scans and prepare to reinstall Windows 8.1. As of now, the hardware seems OK.