I've had the SAM3ha in my sig for a while but I just got it and put it into place this week. To be honest I was having second thoughts as the 4367's sounded so good. My only complaint, and I think it may be due to the way the auto set up make combine the channels, the 4.1 set up was a bit bass heavy. I put the SAM into place, ran the set up again and now I'm back to a nice flat response. My conclusion is for optimum 5.1 or higher you do need the center channel. If you're happy without it fine but you will be surprised at the overall HT performance with the center. There's always variables that could be considered or blamed but I'd encourage you to move up if you haven't.
When I sold my Revel fronts and moved to JBL it's the first time I can recall not having a center. I also preach timbre matching, and yes, all 5 channels if possible. I spoke to a JBL rep who told me the SAM was a dynamite center. I was debating between the SAM or the higher up Array center, I think it's the 880 or 800, so for him to not try to sell me up gave me confidence in the SAM. I've watched a couple movies and it's close enough I can't hear any difference so far. I know there has to be a sonic difference but the horns must blend well enough for HT.