So both the Bonn N8 (which I own) and the SW-8 use customized TCXO clocks. Some report even better results using switches with OCXO clocks, like this one and this one.
To your question, do you really need to spend the money for an "audio grade" network switch - not in my experience. Setting aside the technical reasons that the clock in the switch shouldn't make a difference when feeding a competent server, and also setting aside what it really means to have an "audio grade" switch (i.e., better clock, more expensive, what makes it "audio grade"?), I simply have not heard a difference. I run 45 feet of Ethernet cable from my router to my server. I have heard no improvement or difference between a bunch of stuff I have tried and compared such as:
- Ethernet cable vs. fiber optic cable feeding my server
- Bonn N8 vs. Netgear switch, and
- Small boxes by UpTone Audio and W4S vs. nothing
There are things I am curious about trying such as the Intona Isolators, ENO Ethernet filter, and the DJM Electronics GigaFOILv4–INLINE Ethernet filter, but based on my experience I just cannot make myself spend the money when I cannot hear any problems with my current set-up - if it ain't broke, don't fix it.