Just upgraded to Windows 8 and have been having issues with an IRQL not less or equal BSOD. It happens mostly when I am using the desktop of windows 8. I can use apps and watch netflix for hours without issues, but fifteen minutes in a browser or on spotify seems to trigger bsod.

System:
* 1 x GIGABYTE GA-990FXA-UD7 AM3+ AMD 990FX SATA 6Gb/s USB 3.0 Extended ATX AMD Motherboard
1 x AMD Phenom II X6 1100T Black Edition Thuban 3.3GHz, 3.7GHz Turbo Socket AM3 125W Six-Core Desktop Processor
1 x XFX HD-697A-CNFC Radeon HD 6970 2GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card
*
* 1 x Western Digital WD Black WD1002FAEX 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive
* 1 x CORSAIR XMS3 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 2000 (PC3 16000) Desktop Memory Model CMX8GX3M2A2000C9
* 1 x Crucial M4 CT064M4SSD2 2.5" 64GB SATA III MLC Internal Solid State Drive (SSD)
I use the SSD as my boot drive and the 1 TB for media.
MEMTEST results are normal, so I don't think its the ram. Just updated the firmware for the SSD and that seemed to improve the BSOD situation, but hasn't completely solved the issue.
I have attached a MEGA link to the ZIP of most recent MINIDUMPs.
MINDUMPS.rar (116 KB)
https://mega.co.nz
/#!Plh2RZ6K!eGgcAR24NfLNTpbFqtJxrGEQ7cEpu3gW7IcuBrmZi7U

SYSTEM_SERVICE_EXCEPTION (3b)
An exception happened while executing a routine that transitions from non-privileged code to privileged code.
This bugcheck is generally related to a video driver issue, however hardware memory issues are possible as well.
The dump is verifier enabled - DEFAULT_BUCKET_ID: VERIFIER_ENABLED_VISTA_MINIDUMP
^^ it is however failing to detect a device driver within violation, therefore this is POSSIBLY hardware.
KERNEL_SECURITY_CHECK_FAILURE (139)
This bug check indicates that the kernel has detected the corruption of a critical data structure.
KMODE_EXCEPTION_NOT_HANDLED (1e)
This error typically indicates low disk space, a bug in a device driver or the system BIOS.
After looking at the loaded drivers list, I am seeing AODDriver2.sys which is the AMD Overdrive; also in EasyTune6 for Gigabyte motherboard - Known BSOD issues in Win7 and 8. I'd recommend uninstalling for temporary troubleshooting purposes ASAP.
How long did you run Memtest for? If it was anything less than ~8 passes (SEVERAL hours), run it again.