Hi dude,
I'm in the middle of a bunch of research about this right now and am at that point where I know there is one more piece of data somewhere that completes the big picture, but am unsure exactly where it lies...going to let the research lead me and see where it ends up  :  )

...Assuming 'beauty' is defined as our pleasure response to aesthetic harmony, and employing the embodied cognition hypothesis, it looks like N4 is the most involved in aesthetics, but heavily reliant on N3 and N1, the latter contributing sensorimotor pleasure associations while N4 looks for symmetry and mathematical (or musical) harmony. I venture into this in T12 in context of creativity.

It appears that the sensorimotor taste 'disgust' response features on all levels and serves aesthetics in N4 as well as morality in N5 (which is why we call nazis 'disgusting', and crass art or inappropriate humor 'tasteless'). It's likely that all the sensory modalities are used in this way and it's going to be a lot of fun figuring out which concepts get metaphorized via which modalities.

Ultimately though, N3 is deciding 'for or against', taking all this into account, so it certainly seems that N3, oxytocin and cortisol levels are doing a lot of determining the details of our individual aesthetic tastes. The main sensory modality of N3 of course, is olfactory (and it also deals with some proprioception skills) A main behavior of N3 is making allies; one of our earliest cultural skills.

This is interesting when we consider that persons with poor or absent aesthetic awareness notoriously have a poor or absent sense of smell, poor cultural skills, and a tendency to be physically clumsy. So I would tend to go with you on the CPU, maybe particularly N3, in merging sensory modalities, contributes more to aesthetic awareness than currently suspected. I would expect N6 to be doing the same thing in abstraction, since it has the complementary task for the 'front end' to N3's for the rear end.

If anything more comes up I'll include it in the tutorial. This is certainly a fascinating area of study.
Best,
AR