First of all, for being able to box you need two or three computers/laptop or buy PA that cost you 10$ p/month.
And answering your question, you can never go wrong with SPH/Necro if you're going to solo, and by solo i mean no cp no groups just you and your boxes.
SPS/Sorc are only viable if you plan to play in group/cp, they have really a hard time leveling after 65+ coz no CDL.
But if you don't give a great fvck u can still play then, u will find AOE groups almost everyday in eu primes.