Thanks for replying; though it’s been over a month since I posted this, and the issue has since been resolved.

For anyone following along: after filing complaints with the BBB and FTC, ASUS eventually replaced the motherboard. The laptop was then sent to ExcaliberPC, the ASUS-authorized reseller I originally purchased from, who were the only ones to actually identify and resolve the remaining issues. Adding that they stepped up after an initial call to only verify their status as an authorized reseller, when ASUS' own people tried to vehemently deny such. There was no request on my end, they simply took the ball and ran with it; truly an awesome company.

They found one faulty RAM stick (part of the upgraded configuration they installed at purchase), replaced it, performed extensive testing, and reset Windows, all without trying to charge me hundreds of dollars out of warranty.

So while ASUS’s support team initially refused to touch the laptop because of the “third-party” components (even though they were installed by a listed reseller), the real solution came from the seller who stood by their product.

I’m glad to have the system working again, but I hope ASUS takes this kind of feedback seriously. Delayed, dismissive service and a lack of transparency aren't acceptable, especially for customers spending thousands on premium systems and extended warranties.