I have a 70's ampeg v4b that I use at live gigs. we run the bass through the PA and have done it through the line out on the back of the amp. Does this mean I dont need a DI box? Would a DI box give me a better sound? If so what would be a good one to get. I hear Radial and Countryman recommended a lot but I have no knowledge about these and how they hook up...active/passive.. PLease can someone give me a crash course on these things. I would greatly appreciate it!