The 6N3C-E is roughly similar to the 6L6G/GA/GB.
It is not equivalent to a 6L6GC and shouldn't be used in circuits designed for the "GC" without first consulting with the amp's designer. Some amps may simply wear these tubes out relatively quickly, other amps could be damaged.
In appropriate amps such as my Ideal Innovations Custom 30 monoblocks, the 6N3C-E is a great sounding tube.
It is not equivalent to a 6L6GC and shouldn't be used in circuits designed for the "GC" without first consulting with the amp's designer. Some amps may simply wear these tubes out relatively quickly, other amps could be damaged.
In appropriate amps such as my Ideal Innovations Custom 30 monoblocks, the 6N3C-E is a great sounding tube.