I went from a Meridian with 2.4 V out (loud enough !) to a valved Lector at 3.3V, and although the sound is both beguiling and dynamic, I do wish I could tame the output (into my Naim 552) a little. I tried ECC 83s briefly and in error instead of its ECC 81s and much preferred the s.q. with a seemingly lower output.
If my experience is anything to go by (?) a 4 V output into a normal pre. input is not going to give you much leeway on the volume control. Interesting what CJR says above, which holds water in my opinion. The more output a CDP has, the more 'shouty' it's likely to be; initially dynamic and impressive but ultimately dissatisfying, esp. in a s/s machine. Some heavily modulated CDs I have don't often get played ! Just a thought if it's relevant.