This is ultimately a matter of personal preference. I personally do not recommend upgrading operating systems outside of its current family... win7 home premium to ultimate for example is fine. Win7 to windows 8, I would not do. Oh, its possible, but there is some risk involved.
If you want windows 8.1, I would install a fresh copy. Don't bother with 8... buy and install 8.1 from the get go. While the upgrade (8 > 8.1) is free, you won't have to deal with any of the upgrade hassles. Like what you are thinking.. well let's see. The windows store upgrade for 8 to 8.1 fills your 350mb System Reserved partition to a point that Windows' Back up will not run. Many people have had issues applying kb2919355 (w8.1 Update 1). Are there ways around these things, sure. But if you are not technically inclined and want the path of least resistance, paying for 8.1 is worth it.
While its possible to upgrade, any problems you have now, know or unknown might come along with the upgrade. I'm not trying to talk you out of it, just want to you to consider all the options.
Don't let flashing your BIOS stop you from upgrading. If you need f20e so newer drivers will work with your hardware,
upgrade you BIOS You'll probably need new drivers for all or most of your hardware anyway. You'll need new installers that are compatible with your new windows. Don't think that what worked with 7 will also work with 8.1. Some of it will, but chances are, something won't and now you have a problem or issue to troubleshoot. This is one of the primary reasons I don't recommend upgrading 7 > 8.
Fresh install = less headache in the short / long term. Its just a fact.
Also, it's very important to have a copy of your data. Remember, things don't always go as promised or as planned. Taking steps to protect yourself from data loss is important.
Again, nothing to be scared about, just consider all angles before embarking. An OEM copy of windows is cheap. Good Luck
Helpful links:
http://windows.microsoft.com/en-us/windows-8/upgrade-from-windows-7-tutorialhttp://www.microsoft.com/en-us/windows/compatibility/CompatCenter/Home