Frequent BSOD - SYSTEM_SERVICE_EXCEPTION and exception not handled

Hi all, I've been trying to debug this machine for 2 weeks and I've been failing! It's an ASUS CM6870 running Win 7 Home 64bit.

The machine has had the OS freshly re-installed, memtest ran without errors, checkdisk ran and we saw no errors, I setup driver verifier and saw an issue with AVAST, and removed AVAST, then when the BSODs continued I did a fresh OS install, and reconfigured the machine (it's running in a financing office), I've run stresstests on the CPU and GPU (and then removed and uninstalled the GPU to lessen the variables) without issues, temps are fine, physical connections look good...

If anyone has any advice, we'd be most appreciative!

I've attached two dump files.

==================================================
Dump File : 102314-6037-01.dmp
Crash Time : 10/23/2014 2:10:39 PM
Bug Check String : SYSTEM_SERVICE_EXCEPTION
Bug Check Code : 0x0000003b
Parameter 1 : 00000000`c0000005
Parameter 2 : fffff800`02ebdac5
Parameter 3 : fffff880`08ea9c60
Parameter 4 : 00000000`00000000
Caused By Driver : ntoskrnl.exe
Caused By Address : ntoskrnl.exe+75bc0
File Description : NT Kernel & System
Product Name : Microsoft® Windows® Operating System
Company : Microsoft Corporation
File Version : 6.1.7601.18526 (win7sp1_gdr.140706-1506)
Processor : x64
Crash Address : ntoskrnl.exe+75bc0
Stack Address 1 :
Stack Address 2 :
Stack Address 3 :
Computer Name :
Full Path : C:\windows\Minidump\102314-6037-01.dmp
Processors Count : 8
Major Version : 15
Minor Version : 7601
Dump File Size : 281,672
Dump File Time : 10/23/2014 2:11:42 PM

Today I ran prime95 blend using most of the 16gb of RAM and full CPU loads and saw a new bug check string: INTERNAL_POWER_ERROR. In the past, I had monitored the PSU voltages using monitoring software...which may not mean much.