mike,
have at it. your wattage is high; you are right. however, your spectral output is fine too. bear in mind, while the 20k's may look very blue, they still have all of the necessary levels of other colors in the spectrum, mainly yellows and reds. they are just significantly heavier in the bluer spike (460 n) giving you the bluer look.
i might orient them in such a way to get nice mixed coverage throughout your tank, but go ahead with the acros. you will be fine.
i would do mid tank initially. keep an eye on them and then bring them on up.
good luck to you.