Of course we're talking about matters of taste now, but no, neither design looks too plain for me (my own design is probably much more plain!). I like simple designs that immediately tell visitors were to look. Your WP theme has a great header and I like the fact that the posts are very much to the left of the screen. If you made the index section a little wider and pushed the sidebar to the right of the screen you'd come pretty close to my own page lay-out :-) With a less busy/colourfull sidebar, your WP theme could become even better than that other one (NOT because it's a WP theme, I don't like the standard blog-like WP themes much). On the other hand, the continuing line around your main site theme/template is done well.
But to come back to your initial question, yes I think you can make your whole website in WP (easily). Somewhere under "latest posts" in this forum somebody talks about a photo gallery plugin that may be of interest for you and I'm sure there'll be something of a video plugin that does the same.
(But don't just listen to me of course!)