Actually, you are incorrect about OEM and only one install. The licensing has changed significantly with Windows 8/8.1.
The primary dividing line is how you obtained it. If you buy it and you install it, you can reinstall as many times as you want, on whatever hardware you want.
Only one PC at a time. But you are not restricted to 'install only once'
Buy the DVD. That way, you'll have it for potential future use/reinstallation.
Actually, with Windows 8 (and 8.1), Microsoft has loosened the license agreement for its Windows software. It can still only be installed on a single computer at a time, but should that system fail, you can transfer that license to another computer. This goes for any Windows 8 (and 8.1) OEM software, regardless of whether you purchase it from a store or directly from Microsoft.
At this point, the only difference between OEM software and Retail software is the lack of customer support directly from Microsoft.
I would buy the DVD.
If you ever need to rebuild or recover, having a dvd lets you boot from it and run utilities and recovery apps.
The motherboard OEM tie was a W7 restriction. With W8, that no longer applies; you can reinstall as many times as you want, so long as it is only on one pc.