Is your natural color as dark at the #2 Ash Brown? Or which RC swatch looks closest? Mixing with the Blonde will lighten it, but I don't want it to go too dark. You did mention that your hair got very dark before. Otherwise, that mix should be ok, just be sure to strand test and watch your timing.
If your hair is lighter, then you could always mix Light Chestnut with the Ash Blonde.
I use Golden Chestnut and my hair is med/dark. Just for reference, you can see my pics on my fotki link, pw below.
SF Bay Area, CA * "The Angel-Goddess-Guru of Haircoloring"
3b/c/a mix. medium texture, low porosity
* pw: just4curlies * My Motto: Strand Test!
some hair pics -- gone, but never forgotten.