I too have recommended this group in the past. They performed live at CES 2005, attracted my attention, and caused me to purchase their CDs. They combine Folk, Country, and Bluegrass in a most unusual way, and while they might not be everyone's taste, there are a few cuts that are worth owning.
The "Live at the Backgate Stage" has phenominal presense and the vocal clarity, harmony, instrumental accuracy, and sound staging is way above average. Cut 11 is accapella and the 4 voices nit together beautifully with great focus and separation. Cut 12 is instrumental and captures the attacks and harmonics again with great focus and separation.
These 2 cuts alone would be sufficient as reference recordings to reveal a great deal about a system.