Yes, you have a serious problem.
First I would want to know if the same problem was with Win7? Also no such thing as AMD 6700 GPU.
Whether you want to load Win7 or Win8 I would assume several possibilities:
Have only the boot drive present where you will install the OS. Have only those peripherals necessary to install the OS plugged in. The remaining storage drives and peripherals and even any expansion cards can be plugged in later after you have fixed this problem.
1. You need to update the BIOS to the most recent version from ASUS BEFORE trying to install Win8. Fortunately easy to do on that MB. [I think this the likely problem.]
2. You need to fully wipe the drive and reset it before install. You can do this from the Win8 install DVD by selecting to delete the partition, reform the partition and then quick format the drive. This will make sure nothing is left in the boot sector from your prior unsuccessful install mucking things up. Then clean install. Be sure to have latest Win8 drivers available for your PC....be sure you install ALL the drivers (may be 3-4 "chipset" drivers).
3. Could be a coincidental problem: Boot up and test RAM with memtest86
and boot drive with mfg.'s free diagnostic app.
4. No yellow/red flags in Device Manager
No Problem Devices listed in System Information
under the Component tab?