It's not "needed" if you like what you are hearing. I was doing the same thing but was not happy with the sound. Adding a pre-amp in my system changed the sound that to my ears was an improvement.
Is Pre-Amp needed
Is a preamp needed. I run my oppo 205 direct to an MC275-6 for two channel audio and it sounds good, but am wondering how much better a pre-amp would make it sound. A pre-amp seems necessary for multiple sources, but not for just one source. Would it just be an extra link in the chain or would it greatly improve the sound?