The CS5i's are the first speakers I fell in love with as a young audiophile more than 20 years ago, so I hope you continue to enjoy them. As you know, they are a punishing load for an amplifier, so you need an amp that can deliver a lot of current due to low impedance and sensitivity. I believe the JC-1s would make a wonderful pairing at that price point, with a balanced tonality, authority, and continuousness (in the HP sense).
Unfortunately, I don't have experience with the W4S amps, so cannot give you a real comparison in terms of performance. However, at a broad brush level, I agree with George's characterization with respect to the B&O Icepower amps I have heard (although well implemented versions, like the Jeff Rowland, can sound sweet in the midrange / treble, although lacking in ultimate refinement).
Best of luck.