How to determine my keyboard velocity?

I have browsed the forum the last few days and realized that it is a great database regarding both theoretical and practical matters. So, I thought that there surely must be a lot of members with experience on the following issue.
I am using PQ with my Yamaha DGX 640. All is working well but I am not sure about the velocity curve. When I use the normal velocity curve in most pianos I tried I am not very satisfied with the sound, it seems dull and muddy. When I change to moderately slow or slow the sound becomes brighter but i feel I am losing the base and that the middle register becomes thin. My question is "is the velocity of the keyboard a subjective matter?" I mean surely it is also a matter of taste, but is there an objective way to determine the velocity of the keyboard? For example press a key with some force and observe the midi value 0-127 or some other objective numerical data?
I understand from reading various posts that what I am asking is influenced by many other parameters but as a novice user I think I'd better get down the velocity curve first before changing other variables.

Thanks for your help