Blonde vs. Brunette

I'm at a crossroads and can't figure out what to do. Up until the fall of 2007, I'd been getting my hair highlighted blonde. My natural color is very dark blonde/light brown. Now, I no longer have the income to continue with the highlights and my hair is really two tone. So, should I break down and buy a box of color from the drugstore? If I do, I'm thinking I need to go brunette, although I'm nervous it won't be close enough to my natural color and I'll end up messing up my hair...