You will get full torque across most of the RPM range of operation. HP is a measure of work based on Torque X rpm / 5252.
A full blown servo would be the Cats meow BUT you can also get full torque with an invertor rated AC motor and a good VFD
3k is really too slow for productive alum work you need to get to at least 5K and 6K would be better BUT you will start making heat in the Spindle at that point unless you replace teh bearings with high quality bearings and Grease.
(;-) TP