Expand bar below header to take up whole width of window

Hello,
Is it possible to expand the size of the horizontal bar below the header so that it expands to both ends of the screen?

Something similar to this perhaps?

.site-header { border-bottom: none; }

The other question I have (which is a bit more complicated) is whether it would be possible to draw a box around the header in the same thin, blue line as you currently have below the header?

Thanks!!! I love this theme!