Question about developers

Thanks, today I did a few things...figured out, on my own, what level color I am naturally and what I'd like my end result to be and figured out what I'd need to use. THEN went to Sally's and asked the salesperson there what they suggested and she suggested the SAME EXACT color and tone and developer--without me even saying what I thought I needed first. So I feel confident I bought what I need. I bought the ION Color brilliance brand that she suggested. The ION website is really cool--very helpful charts & info--check it out: http://www.ioncolorbrilliance.com/home.asp

I tried to color my light brown hair to a light ash blond using Clairol Nice n' Easy bought at a drugstore. I understand the developer in the store brands is only 20%. It barely lifted my brown hair two levels--stopped at orange. If I buy a 30% developer at Sally's, will lifting it one more level (3 levels as opposed to only 2) get me the color I'm trying to go after?