Nothing thrashy or symphonic about Extol. They've always been progressive death. Their new album is definitely a must either way, much more melodic than their very early works. Immortal Souls is a decent christian metal band with melodic elements too.
a couple years back, 3 of the Extol members put out an album under the name "Mantric" -- this is very progressive / melodic, less brutal than a typical Extol album. i perceive you're a fan, zaoman, if you haven't heard this, you definitely need to check it out. you know there was a second Lengsel album a year before that, too? good stuff.
Stavesacre may be worth checking out for fans of killswitch engage, too. don't know why it didn't occur to me earlier.