So for one, the sp200 is poor at recreating space, which makes the clear sound rather boring in terms of spatial recreation and it causes it to sound pretty congested and 1 dimensional. Another issue is the added over sharpening in the treble that the sp200 adds, which is kinda unpleasant imo, and sounds off on the clear. Something else is timbre, on the sp200 it’s pretty mediocre and coupled with the clear it sounds somewhat unnatural. The clear also does take well to scaling to a higher quality amp to get more overall performance out of the unit.
The rnhp is a good match imo as it has accurate timbre that make the clear sound more natural and alleviate the issue that some have with the clear on the wrong amp being metallic sounding. The rnhp also really improves spatial recreation, and preforms well with creating an accurate space with the clears which is pretty immersive. The rnhp also is more neutral than the thx to my ear, where the thx is more analytical, but the rnhp also ends up having more detail and better technicalities.