Excel can work pretty well in tanks where you can't or don't want to supplement with CO2 (if the plants need the CO2 in the first place). Beware: it's toxic in certain concentrations to most invertebrates.
When it comes to liquid ferts? You're paying for water. Why not buy dry ferts and mix your own (there are handy fert calculators all over the place to help you - as well as this forum) with some distilled water? That'll work wonders.
If you're dead set on buying liquid ferts, consider buying from one of the forum sponsors so you're getting more bang for your buck.
Besides Dry Ferts though, what are your opinions on API Liquid Plant Food or API Co2 Booster or Flourish Excel?
Is one better then the other, should they be used together?