I personally do not like Saxon, I do love spiral approach curricula though. I would recommend both Horizons and Singapore. (I actully do them together) Singapore is great for teaching concrete, and excellent for mental math. Horizons is a GREAT spiral curriculum (but you NEED the teachers manuals)
Other great math programs for you to check out would be Math U See, Mammoth Math, Key To series, Life Of Fred (I will be starting Life of Fred with my oldest daughter this summer, fractions, and decimals & percents)