Recommendation: Complete my studio monitor system with a center channel

mrdoug1, I think you would be better off talking to the theater crowd. Most of us think in two channels only.

It really depends on what you want. When you say twice you really are in love with that Yamaha Natural Sound, that is a trademark not actual natural sound. Furthest thing from it. But there was a time I was in love with JBL sound, and solid state, and looking back there were several times I rejected vastly superior components simply because they didn't meet my preconceived notions of what should be. 

So if you really want to bask in that YNS, then what you want is a center channel very close in sound character to your L/R speakers. Whatever they are. I can't get into it enough to recommend one. 

Because when set up right the center image is so rock solid there are few things more superfluous than a center channel. I had a guy one time so convinced I had a center channel he went and lifted up the blanket I had covering the TV, so sure he was that there was a speaker hiding under the blanket. Walked right up to it convinced the whole time it was hiding a speaker. Think about that for a minute. That is how little use there is for a center channel speaker. 

Unless of course you are convinced you need one anyway. In which case, your cave, your system, your choice. Go for it. You know what you like, and that is the First Audiophile Commandment: Know Thyself. 

Your best match would be to find yourself a single HS8.

Agree a single HS8 would be your best option.