Definitely Stryper (I haven't gotten around to collecting their music yet (only youtube for me), but I know they are THE Christian band of that era, and I have been lucky enough to hear their music on a good old- fashioned LP)
Petra is also good, and well known
Narnia is a band I haven't heard enough of to be certain, but it seems they are very similar to Petra
PS: If you find one band you like, go to last.fm, look the band up, and click "similar artists"