I like the bar that says "Welcome Back" with the "send Home image".

Maybe you should take that and make one that is a little darker or make that current one that says welcome back darker and place the nav bar on top of the second bar so they are on top of one another just one is gray the other is dark gray or black.

Don't show your admincp link on the site. Also rename it to something that is harder to find. This way you can help avoid hacking. Have you considered using a template instead of designing your own?

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You have the bottom bar that says "Welcome Back".
You have the Home, Download, ect.. Bar.

What I am saying is why don't you take the bar with the "Welcome Back" and utilize the design for the "Home Downloads ect". Have the bottom one a little darker than the second one and place them on top of one another with a slight space between another vertically.

A little clearer?

For the site your building I recommend using wordpress. It could make your site look sick...

Just look everywhere to get your own ideas that will be easier

Not so much with the backround, you need more objects on the site itself, the logo in the top corner looks very attractive [; but the rest of that main banner is well... blahh... my opinion, put other things on that such as a motto or something. Fill in the extra space! too much space on a website will encourage people to leave.