In combination with my headphones line-out always gave me a weird soundstage, positioning wasn't accurate. This might also have to do with my opamps, OPA2228, that improved positioning/soundstage while using headphone out, but line-out certainly didn't sound right in my case.
I'm having huge issues with disconnects at boot lately though. I've been using the same mainboard for quite a while now, one that has UEFI, just as Windows 8. The issue does seem to get worse though.
Is it plausible to think the soundcard needs a certain amount of time to "get ready" during boot? I'm not using any of the "super fast boot" options of Win8, as my SSD isn't formatted to use it, but booting still doesn't take very long (to say the least).