Thiel has worked with Madisound since the 1970s, so they know that we want unflavored, technically accurate caps and resistors. I went to them for advice for my PP rebuild and they recommended Mundorf as the "winner" in their customer experience. Mundorf has a deep range of solutions and I have not yet chosen mine along their continuum. Thiel routinely bypassed good Solen PolyPropylenes with a smaller value of Styrenes. Styrenes are very expensive due to manufacturing losses; they have been replaced by higher-performance PPs. We coveted, but never used in my time, Teflon bypasses which are extremely clean, neutral and stable over a wide current range. If I were hotrodding an upper end Thiel, I would consider a Teflon bypass in the tweeter feed.
My "lost" post included a note about hookup wire. I have seen people "upgrade" Thiel hookup wire. I don't buy it. Thiel (lexington) hookup wire is 99.9999%, long crystal, teflon jacket, 3 twists per inch. I've never heard or measured better from any boutique / branded wire. The only thing I am considering, because I must increase my lengths for my outboard crossovers, is Paul Spelz's AntiCable 3.1 for hookup wire. It is high-grade copper with only enamel insulation, similar to our six nines coil wire. Dielectric absorption is the problem. Teflon is great. Less coating is even better.