Autospec,
I suspect you have been out of touch with the boutique cap market for a few years. InfiniCaps (and WonderCaps before them) are quite dated and no longer in the running for a high quality coupling cap, IMO. The regular Mundorf Supreme is a fairly inexpensive cap that I like a lot but some people will find it too colored. It is a very warm and slightly opaque sound but very musical and very dynamic. The more expensive Mundorfs like the Silver, Silver/Oil and Silver/Gold/Oil all offer a more extended high-frequency response with more detail and more transparency, but the tonal balance is not as natural to my ears as the standard Supreme.
If your budget has a bit more room, my very favorite coupling cap is the Copper V-Cap (CuTF). It has the best combination of sound qualities of any coupling cap I have tried, and it excels in the areas that are most important to me: neutral tonal balance, excellent detail and excellent dynamics. Out of the 20+ coupling caps I have tried over the years, this is my favorite. Some folks prefer the Duelund CAST to the V-Caps, but I consistently prefer the V-Caps (either TFTF or CuTF versions).
I have not tried the Jupiter copper foils (contrary to Charles' post above) but they also have their fans.