Premiere Pro :: Slow Render Times With Large JPEGs - Complete System Lag?

In a project i'm working on I have two large jpegs with a small zoom scaling effect. Going from 100 to 103 percent.

I've noticed that both Adobe Media Encoder and Premiere Pro experience a heavy slow down in render time as soon as the jpegs have to be rendered. Not only does the render speed almost come to a halt, the complete system lags very heavy, even the mouse cursor won't respond well.
 
This happens when i have GPU acceleration enabled and when i do a 2 pass H264 encoding. When I have the GPU acceleration disabled the render goes very smooth, and doesn't seem to slow down...
 
The jpeg is 4023  x 2677, and 6,97 MB large.
 
Scaling the jpeg down to about 1920x1080 in Photoshop and put that one in the timeline made the render go a lot faster.
 
I understand that a large picture takes a bit more time to be rendered, but we're talking about a 10minute render whit the large jpeg file and  a 2 minute render with the jpeg resized. The total time of the two jpegs in the video is 5 seconds in a 3 minutes video. So, that made me think that the render times are exponentially long.

Is this considered normal, I can't remember having such big differences in CS5.

My system:
 
 Premiere Pro CC (latest)
i7 4930K
32 GB RAM
2xGTX480Footage and project on a Raid0 disk
Previews/Cache on a Raid0 diskSystem and Premiere on SSD
Render to a single 7200 rpm drive.