Hey junior, I ordered a pair of 580's this week, should be here in a couple days. Considered the 590's but would be kinda big for the room. Wondered how the 550P is doing with the 580's? I'd imagine I'd want to set the sub x-o as low as it would go (50 Hz) or nearly so. Any sub would have a hard act to follow, since I'm used to the excellence of a REL Stentor III.
But I've read of reliability probs with some of JBL's previous self-powered subs, i.e. the amps burning out prematurely. As you probably know, Harman is run by bean counters now. It's not the JBL of old, except once in a while they make a decent line like this 500 series (designed by Greg Timbers).
Also, have you experimented yet with raising the 580's a few inches to get the horns' center closer to seated ear level? I have a feeling that's what I'll be doing.
Anyway, grats getting the cherry version (sick of everything in audio being black). I can't find them anywhere but overpriced on the Euro or Japan market. Seems they're all sold out in the States, and won't be any more since JBL has discontinued this series.