If you have already exhausted the maximum size in the filter settings, then no, there's no way to expand them even further. You will have to work on a lower res version of your image and then somehow scale it up or at least use a scaled up version to overlay it with blending modes to transfer the structure.
Thanks for replying. I already tried to work on a low res version and then scale it up but then, we can see the shape of the pixels.. I also tried the second option but didn t get what I want.
I m really surprised there is no way do such simple thing on Photoshop...