I used to own and gig the R600 and those Carvin 10's all the time.
The cabs are nice and punchy. Lacked the real deep bass. My 15 at the time (also a carvin) really did add more lows. Came to find out though the 10's sat in the mix pretty nice out in the audience, just seemed a little bass shy up close. Lots of sub-bass on stage usually isn't a good thing.
The amp was alright. I didn't like it as much as the old Carvin PB500 I had before it. That one had more "balls" or "girth" for lack of better words. The redline was more neutral, some would say "sterile" amp. Others would consider it a blank slate on which to paint....they'd both be right.
It'll only do clean no matter how you twist the knobs. Any sort of flavor has to come from external effects. For a built-in compressor, that feature was actually useful. Got some range there for mild compression effect where a lot of other amps built in compression is basically squish or nothing.
It does have a tone of eq and various patching schemes, and fully biamp capable. That can be cool for some of us, but it's not user-friendly for newbies or simpletons. At a church, presumably with a wide variety of players, including the inexperienced or not technically adept, there is a lot of opportunity for things to go haywire in all those controls.
The vertical stacking of the cabs does have very noticable advantages out in the audience. Namely wider dispersion of the uppermids and highs, more even/consistent sound throughout the audience, as well as having a speaker or two up closer to the players ear level, so they can hear themselves better without cranking the volume too much. It also makes it easier for them to hear their uppermids and highs as well. That could cause some cranking of the bass knob as the inexperienced will tend to turn up what they want to hear more of instead of turn down what they want to hear less of, all the while making those judgements from a few feet in front of the rig instead of out in the audience...where it actually matters.
