034 Motorsport and I believe H2Sport both do a Spherical bearing bushing kit, but they are obscenely expensive.
I am wondering if I use the Whiteline bushing kit as I have Whiteline bushes and RSB on the rest of the car. Its 1/4 of the price.
I guess I can hold off and get a Spherical kit further down the track if its really going to be worth it though.

I asked 034 what the difference was and this is their reply below, but I cant see why Whiteline would release something that could cause potential issues as they usually have a very good reputation..

..polyurethane is a terrible choice in this application.

Even the stock rubber bushing is a better choice than polyurethane, because the bushing needs to be able to function in shear to let the suspension articulate properly.

We use a spherical, which does not deflect at all, but allows for full articulation.

The stock bushing uses rubber, which allows for articulation, but introduces a significant amount of deflection/slop.

The Whiteline kit uses polyurethane, which does not allow for the suspension to articulate properly, but offers reduced deflection. Since polyurethane is only effective in compression, it will eventually pack and wear.

034 Motorsport: Rear Trailing Arm Spherical Bearing Upgrade Kit, Volkswagen MkV/MkVI and Audi 8J/8P - 034Motorsport | Performance Parts for Audi, Porsche, and Volkswagen

Whiteline: Whiteline