Your current set-up is far better for power computing than the Llano A series APU, which is for a low cost entry level PC.
You can get Prime 95 errors for many reasons. I'd make sure the RAM and Vid card are properly seated and run Memtest86+ from a floppy, CD or flash drive to be sure there aren't issues with the memory. Also make sure the RAM voltage and timings are correct as 16 GB. requires everything to be perfect to prevent errors.