Logo image Header

Hello, can some one help me, i cant change the size of my header logo,
i dont whant to make the white bar bigger, i just whant to make the logo bigger it to small, ive used css plug in but it only made the white header bar bigger along with the logo.

the other question is if i can add an image over the image of the background, i whant to add the logo over the background it will be postitioned on the left top corner under the white header bar.

heres the link to my webpage: torus4x4.com

thank you, im looking forward to your comments.