try a kawasaki or gator magnum line
i have a Kawasaki and its one of the better trimmer's i've ran,,,redmax, hoffco ,older homelite's, dolmar and yes ive ran the sthil combi unit....... i just dont like the weight myself,,,,but most people dont use them very long and you have more attachments .....all of them cut grass............the Kawasaki kt 27a is 1.5hp and 10# and i like it......... i use gator magnum aramid core line.. it is tuff............the string is one thing that makes any brand cut better........my friend is a sthil dealer and i trim for him..be supprized how fast weeds grow when ya work on lawn mowers,, sometimes i test the repaired trimers for him ....... i usually judge them against my Kawasaki......... i was trimming the really growed up stuff the other day with my trimmer, waist high grass no problem.... power and real good string