Wery carefully. You need HSC speed (rpm) and you need HSC feed and good acceleration. The complete is HSC machining.
Bigger RPM you can use for small dia of tools. Good Luck Libor Pírko

There is a huge amount of information available on high speed machining of aluminum.  The following articles all discuss various aspects, and should help point you in the right direction:

http://www.mmsonline.com/hsm/articles.html

http://www.ctemag.com/article/viewArticle.asp?ARTICLE_ID=241

http://www.manufacturingcenter.com/tooling/archives/1202/1202cuttools.asp

http://www.automfg.com/articles/029804.html

http://www2.coromant.sandvik.com/coromant/products/die&mould/new_pdf/HSM.pdf

http://fstroj.utc.sk/journal/engl/papers/034_2002.pdf

If you have trouble with low revs that result in low cutting speeds,try if possible to use larger diameters of cutters.With the adding of a high speed spindle you dont solve the problem really,if your machine is not able to accelerate and diccelerate and run at the programmed feed rates you could have some  or a lot of problems.If you run high  revs up to say 30-40,000 revs/min but cant increase the feed rate that suits the cutter geometrie being used you could have some big problems with the average chip thickness.High revs and low feed speeds will result in a lot of heat on the cutting edge and this could result in the aluminium sticking to or welding to the cutting edge.Best results with coolant are with mist cooling.Kind regards,Speak with Seco Tools,