I have Undeceived too, I bought it because it received a rating of 95/100 in Aardschok and I heard a track of them on mp3.com before, which I remembered liking.
I am usually pretty hesitant towards christian bands, because many have this annoying preaching attitude, but I think Extol are one of the few christian bands who's music doesn't sound very christian, if you just ignore the lyrics, you won't notice.
Listen to the vocals, the raw vocals are great and really dirty, I like the clean vocals too and the violin parts are nice.
Basically I think every fan of high class melodic (Death) Metal should check them out.