who makes a decent center channel speaker?

Another center worth mentioning is the Dunlavy SCVI...stacked vertically for best dispersion, of course.

"I would stick with the same brand as your left and right channels" (Mlawitm)

"Not only with the same brand but as similar to the L/R speakers as possible. I prefer and use three identical speakers across the front" (Kr4)

"I second Kal - same brand and even better if same type" (Shadorne)

I wouldn't even think twice about using a different center than your mains! You'd be better off either with no center at all, or using some other combo of L/C/R speakers as your multi-channel setup, rather than mixing and matching speakers across your front, yes! (it's basically like haveing a different left and right speaker in a stereo setup - you wouldn't do it).
I basically disagree with the line of thinking of getting a "good center" to go with your mains. This is a SURE way to end up with an incoherent, totally unbelievable soundstage, different sounding pans across the front 3 speakers - drawing you out of the illusion of one soundfield! And yes, every professional audio reviewer will agree here. But, you make your choices, and live with your results, either way.
So what are your left and right speakers, and what's your setup like now?

"Unfortunately, the construction of the vast majority speakers is faulty BY INTENT as they cater to aesthetics and convenience rather than performance."

Faulty by Intent? Um whatever "faulty" means. I've known enough high end speaker manufacturers to know that, at least with reputable hi-end makers, that there certainly isn't any "faulty" built into ANY speaker they make! That's my experience. In fact, the better speaker designers, if they do make a dedicated center speaker offering, spend time to ensure that the speaker is designed, matched and voiced to go with their products, at least.
As for different manufacturers, my experience from having sold/installed dozens and dozens of different speaker products over the decades is that THEY ALL SOUND DIFFERENT! That said, wisdom simply tells me that you have a much much better chance of putting together a cohesive, properly matched set of speakers, if they're from the same manufacturer, specifically ones that are designed side-by side with ones they're trying to mate with.
But hey, sounds like most here are all for you matching whatever otherwise "good" speaker you can find. Well, it's a choice. I mean I guess you could use 3 of the same tires on your race car, with one odd-ball, or wearing one shoe different than the other, if you like. Don't get it.
I've been doing systems both as a hobby and professionally for almost 2 decades now, and it's been a life's work for most of it - learning to build better systems and such.
So my advice is obvious, but you walk it out, try some things, and see for yourself, to be certain(if you want to know that is).
Like I said, not only does my experience tell me otherwise (Lord knows I've tried many many mis-matched speaker setups in my years, and learned eventually), but yes, all the speakers in a system should ideally be the same. I mean you've gotta be missing something if your thinking tells you to use the same L/R speaker, but then it's ok to add one in the middle which can be different!!! DOH!
Um, well all I can say is that, especially in this case, indeed, "the crowd is always wrong" (unless you're talking about sales. LOL). Basically, if you value quality, I'd go with what the pro's suggest. And they surely would NOT be recommending just go out an get some good speaker to put in there.
Nevertheless, let us know how it turns out.
BTW, if you do decide on going with some other brand center, and you are sifting through the advice being recommended here, how will you know who's suggestion to take?..I mean which ever choice sounds interesting?! Um, OK...?

"If you had to, ARC or Audyssey will compensate greatly but not entirely."

Amazing. What's being inferred to the uninformed here is that these DSP processing technologies will make all speakers in your system sound the same, regardless of make, model, manufacturer, etc! Well you could call Audyssey and ask em if this is the case. I've been to their training. Let me assure you a forehand that that IS NOT the case!!
You can't expect to use whatever speakers you want all around the room, mix-match er whatever, and think technology will do all the fixing and mating for you. Nonsense I say! Anyway, that's what's coming across from this tone here.
Well all I have to say is that those advocates here (majority - amazing to me as it is...WOW!...WOW!!!) of using whatever "good center" you can pick up, is that you are certainly contrary to the pro's who make their living eating and breathing this stuff, and who've been in this passionately for decades! - and they have always preached matching speakers, ideally identical if you can. Getting into other technologies will only lead you astray, my friends. But invest and build at your own peril, I say. What is wisdom? You be the judge here.
But hey, if any here want to chose other paths, it's all good. What's fundamentally sound judgement? Well I've been deep into this stuff for almost 2 decades now, and I am still learning things new all the time! So what chance has ANY audio newbie out there who's taking ill-advised recommendations got of figuring out how to "build a better audio mouse trap"? Might as well just get whatever and hope for the best, cause a solid starting foundation and fundamentally sound choices you will not be making! Of that I can assure you.
Like I said, if I were looking for solid investing advice, I wouldn't be going to those who never got anywhere, financially! Nor would I be going for medical advice from someone who read a couple of articles in a "Better Health" magazine. Or for that matter, asking advice on how to rebuild my automatic transmission from someone who's only done and oil change and brake job!
Well, I made my point. Personally, if Phasecorrect decides to go the "whatever is good" route, I think maybe the best route here would be for him to go out and by whatever center he thinks sounds good in some system he auditions over at Best Buy! That way, when it doesn't work down the line, at least he can return it. Now that sounds like more sound advice. Lol. At least you know BB is going to be there over the next 90 days when he finds out this theory is no good.
I'm just simply blown away here by how the majority of those chiming in here all believe contrary to people who've invested blood sweat and tears into learning how to do this stuff right! I mean I'm befuddled. Really I am. To me the responses here are nothing short of the equivalent of having everyone you talk to recommending you go to the local "psychic adviser" for all your financial decisions!!!
DOH!

I've since reformed my "critically accurate recommending ways" here. I've apparently missed the question - running off on my own tangent. To that, I apologize.

Good center speakers: NHT VS2, NHT Audio Center 2, Paradigm Pro Studio, Mcintosh HT-1, Infinity MTS Center, Wilson Watch, B&W Nautilus HTM2, KEF Reference 202/2C & C200, Meridian DSP7000c ($?) Dynaudio Evidence ref center (a little pricey).

If I've left any good candidates out, I'm just a little fuzzy on some candidates at the moment. But the above should "get you buy" otherwise.

Yes the question was indeed posed, "who makes a descent center channel?". While you do not for sure need to endorse the speakers I have listed, it is most accurate to state that those are abslolutely, possitively, most assuredly "descent center channels!" Whould you argue that point? That's all that's being asked here....not weather any particular speaker is a good match with some other invisible speaker in a given system.
My list stands on it's own merit.

Personally I think someone should call Dynaudio and Meridian and inform them that Kr4 is not endorsing their $22k center speakers! They may be a little dissapointed...

"Yes, they come from decent houses." Kr4

"Descent houses", ey? LOL. Well, they may not be as "descent" as say, the number one selling speaker brand in the world (B.)
But hey, I'm sure they can at least throw a little somethin' together that you ought to be able to hook up to the center channel connection thingy in the back of one's receiver, right?. Which, in the end isn't that all that matters?. Cause you wouldn't want to have nothing connected there, when they went out of their way to make a thingy there in the first place.
I always say...

Oh I forgot one more. Ya know who else I think makes a descent center channel? Vandersteen...

Ok, phasecorrect, so I'm curious. Have you narrowed down your selection any? What speaker are you leaning towards buying now? Did any of this help you decide? Personally, I would opt for the Dunlavy SCVI for the money you'll save over the Dynaudio at $22k. But that's just me. I am, however, 1000% certain the performance specs and ratings are going to be higher for the single Dunlavy SCVI over the Vandersteen center you're considering.
So which is it, which is it, which is it!?!...