I've had the h8-1414 for almost a year and use it for gaming. I replaced the PSU with 500W Microcenter Inland Gold, no issues. I replaced the original video card twice, first with a Gigabyte GTX650, and later with an XFX Radeon 7870 Black Edition. Both worked with no problem and, despite what most correctly say about Win 8, I did not have to change anything in the BIOS to make either card work in my machine (pleasant surprise).
I have not upgraded to Win 8.1, but an error message about disk failure or missing boot disk is more indicative of a problem with your upgrade or your hard disk. You should not need a new motherboard. Are you able to run any diagnostics at all?