Nevs are a good all-round tyre. They are not the fastest or the grippiest, but that's because tyre design is always a compromise. You can go with something faster in summer, or something better in mud in winter, but they will do most things well.
If you find the rolling resistance of Nevegals is holding you back, then you probably need to MTFU and blame your legs not the tyres. Unless of course it's mid summer and all your friends are riding slicks or something...
Don't put a stick-e on the back. Unless you ride particularly hard, or lots of rock, don't put a stick-e on the front either! (IMO of course)