should I upgade my Nakamichi PA-5?


I have a pair Proac Tablette Reference 8 Signature with Sony 9000ES & Nakamichi PA-5 using in a small room. So far nothing wrong with them. I just wondering should I change to PA-5II or PA-7/7II? is there any improvment? and what kind? thanks.
leoweng
Thanks Jaybo. I used have CA-5 Pre-Amp with PA5. Just because digital input, I just bought this SONY 9000ES. Did I make a mistake??(I still have that CA5)

And Thanks Bachtovinyl. I wish I clound come over and listen to your Magnepan. But I live in So. California.
i understand the sony 'may' sound fine without the pre. it would be interesting to find out how the sound changes with the pre in the system.....the sony is quite good.
I am sorry something missed there. What I have are Sony TA-E9000ES AV Control Amp (Pre Amp.) and Nakamichi PA-5 Amp. now