Update. The power supply that came as part of my newegg bundle arrived. I got that installed in my wife's PC along with one of my evga 970's. She has a dual monitor setup and didn't want to loose it so I had to leave the older radeon 6670 in there as the 970 had two DVI ports and two hdmi's. One of the monitors (the junky one) uses the older VGA with not other options for connection.

I do not see her PC running any GPU tasks. Is this a coincidence that there are no GPU tasks or does BOINC not like having two different brand GPUs?

You need an cc_config.xml file that tell Boinc to use all the gpu's it finds in the machine before it will use both gpu's all the time.

This one will work great for that:

<cc_config>
<options>
<use_all_gpus>1</use_all_gpus>
<report_results_immediately>1</report_results_immediately>
</options>
</cc_config>

Copy that using Notepad in Windows to the Boinc folder located at c:\program data\boinc and save it there. Then in the Boinc Manager go to Options, read config files and Boinc should start using both gpu's right away assuming MilkyWay still supports both of your gpu's.

The dip could just be a couple of units finishing at the same time so the gpu is slightly underused as it switches to the next task.