Customized JetPack Top Posts & Pages Thumbnail Quality

I’m utilizing the TOP POSTS & PAGES (JETPACK) widget in a customized area added to our Blog’s home page. I’ve added it and styled responsive changes to the thumb that occur at 650 and 450 pixels but I notice that the image quality for these thumbnails is EXTREMELY pixelated. If a reader clicks through to a story from the home page stream, they will get the standard TOP POSTS presentation in the sidebar on the right.

How do I control the thumbnails quality of the images and add these two new sizes without effecting the standard preso on click through pages?

• Staging site @ http://joesimpsonj.wpengine.com/
• Live site (without new section) @ http://thesource.metro.net/

Thanks in advance for your attention.