Care to elaborate on the bit//flutes/feed/plunge/RPM used?
What are the symptoms when the carve start to give up?
The Dewalt, provided it is healthy, is powerwise plenty capable for alumimium. Aluminium on the other hand isnt a straight forward (compared to i.e wood) material to work with, with a much narrower work envelope and less tolerable to lack of stiffness/slop.
Like Neil, I dont think a new router is your solution - your issues lies elsewhere. To help you further more specific information is key