No such thing as a "Decent" Pure POW mag, because Power is nothing without Accuracy. Generally, you want to pump your mag's dex up to whatever it takes to max out your class's ATA at level 200 (you can subtract a point or so if your class requires v101), and then dump the rest of the mag's stats into your primary attack set (pow or mst if you're end game FO who needs ATA on their mag for Demon's/Hell)