Excellent points, thanks for the reassurance!
I thought about just waiting for the Studio 6 center as I'm not really in a hurry. I'm also considering other horn center channels, such as the RP centers. Presumably, I should stick with a horn design at least. Correct?
I fiddled with the crossover a bit, but in the absence of a sub. I was trying my best to judge the upper frequencies on the 520c vs. the 590. I could possibly cross it very high and give it a tremendous dB boost and be mostly satisfied. But I'm aiming for a higher level of satisfaction for now.
In other news, JBL customer support is great. They are going to send me a replacement so I can determine if my unit is defective or I just don't like it. They also agreed to extend my 30 day return window so I can have adequate time with the replacement.