I think it looks better with the spacing between the buttons and banner as well.
HOWEVER, if you still want to try getting the buttons and banner as a solid, here's something you can mess around with.
Use a 1 pixel image that blends into your back as the picture for each of your buttons. Go into "Banner Area" under "Advanced Style Settings" in your Styles & Colors page.
Put your button graphics in there attached to the link for the page they lead to. Mess around with it, see what happens. I think you can do it so there's no space at all between the banner and buttons since you are using the $Block[bannerimage] tag.
I was thinking about doing that.. Would anyone be able to tell me if the links to the different sites change?? The only issue I see with using the banner area markup is that it has to be different for each page since there are states for the buttons.. such as Active, Inactive, and Rollover. I know how to do that on pages I'm designing from scratch, but seeing as the $block[bannerimage] tag just inserts that image, and I have no controll over each page.. the scripting would be a bit of a nightmare for me to do and get the image states set properly when viewing the individual pages.. I think I'll just leave it as it is right now..
Thanks again all for your input, and I'll be updating my box borders shortly. I'll post here once they are complete to get some more critiquing =P