For fear of scaring off the OP with this discussion, I just want to briefly add that I recently bought a GoldenEar SuperCenter XL. It was already broken-in as I am the second owner. My entire current setup consists of JBL Studio 5's, and I've had everything from Monoprice HTIB satellties all around to HTD Level 3's and 2's to BIC FH6's...and I have a sordid history with mixing and matching. Now that my ears are trained to appreciate some
sonic characteristics among different brands, I can say that a horizonal center (specifically the SuperCenter XL) does NOT pair well with the Studio 590 towers I have as L/R. The SuperCenter has a noticeably different sound (even with dialog), and that might be because I'm used to the 590's that have been up for most of this year.
Zorba helped me out a few years ago when I was starting out and sweating the idea of a mix-matched LCR. He talked me down form the ledge and ultimately I was fine - and even happy with - a varied front stage. But now? GoldenEar is no slouch of a brand, but it just doesn't work with the JBL towers. When playing a video game (in this case, Aassassin's Creed Odyssey) that has LOTS of dialog that is constantly moving around you, voices carry across the LCR and you can just tell that there's a different sound from L to C to R and vice-versa. The voices almost seem to be more present in the GoldenEar, perhaps more "full"? It's hard to describe, but this isn't a bad thing in of itself! I'm also not saying that the JBL's are coloring the audio in a negative way...they just have noticeable
sonic signatures that do take you out of that scene or moment, even if only for a brief second. It should be noted that the two brands are using entirely different everything, from tweeters to woofers to crossovers.
Before the SuperCenter, I was employing a phantom center since the 3rd tower I want to use as my dedicated center channel is too big for the space at the moment
OP, this is one of those things that you can read for hours and hours on and still have NO frickin' idea what to do. You just have to try it out and see how you
like it. I would say get the 520c, if only for matching aesthetics alone. I'm sure I'll be burned at the stake for that one