** Important Notice:
- If you own a horn loaded center speaker (Klipsch, JBL, etc.) you are good to go

- If you own a coaxial center speaker (KEF, etc.) rest easy

- If you own any MT, MTM, etc. speakers and they are placed vertically, perfect!
- If you own a speaker that looks like a center channel, but all drivers are aligned vertically (2-way, 3-way, etc.) then again perfect!
- If you own an MTM speaker and it's placed horizontally, but has the tweeter on top, or severely offset, you have the lesser evil...
[ADMIN] You generalize way too much about center channel designs. What matters most is how the speaker measures and sounds in a real room along with how it's being used.
Suggested reading: Vertical vs Horizontal Center Channel Speaker Designs
Wait for it...
- If you own a traditional LCR (MTM) speaker and it's placed horizontally, then it's definitely time to upgrade
This is a great article which describes the problem perfectly:
Center Channel Speaker Design Additional Considerations — Reviews and News from Audioholics
The following center channels are all 3-way, where the upper midrange driver(s) and tweeter(s) are aligned vertically and crossed to the woofer(s) at a low frequency (approximately 400Hz).
This is the only way to have a proper horizontal center channel speaker

If I missed anything on the market, please let me know!
** End Notice
Asperion Intimus 5C Center $280 (not recommended)
Aperion Intimus 5T-DB Hybrid HD Speaker System Measurements | Home Theater
Infinity Primus PC351 $280 (no anechoic data available)
JBL ES25C $350 (not recommended)
JBL ES20 Speaker System HT Labs Measures | Home Theater
Jamo D 500 LCR $350 (recommended, THX Select 2 certified, no anechoic data needed)
Paradigm Center 1 $380 (no anechoic data available)
NHT Twoc $400 (no anechoic data, but not recommended due to ThreeC's performance below)
JBL LC1 $400 (no anechoic data available)
Revel C12 $500 (fantastic)
The Revel Concerta F12 Surround Sound Speaker System Measurements | Home Theater
NHT ThreeC $500 (not recommended)
The NHT Classic Four Surround Sound Speaker System Measurements | Home Theater
JBL LC2 $500 (no anechoic data available)
Jamo D 600 LCR $600 (recommended, THX Select 2 certified, no anechoic data needed)
Paradigm SE Center $600 (no anechoic data)
Paradigm Center 3 $600 (recommended)
Test Report: Paradigm Monitor Series 7 Speaker System | Sound and Vision Magazine
Energy RCLCR $650 (no anechoic data available)
Asperion Verus Grand Center $700 (not recommended)
Aperion Verus Grand Speaker System HT Labs Measures | Home Theater and
Aperion Verus Grand Center Overview and Measurements — Reviews and News from Audioholics
M&K S-150THX $750 (recommended, THX Select 2 certified, no anechoic data needed)
Polk Audio LSiM704c $750 (no anechoic data available)
Paradigm Studio CC-490 $850 (no anechoic data available)
The above list has been ranked by price. As you can see, there are literally only a few good center channels being sold today. It's unfortunate

I hope this list helps someone decide in a purchase of a center speaker under $1000.
The only recommendations are for the Jamo D 500 and D 600, M&K S-150, Revel C12 (probably the best there is), and maybe one of the Paradigms.
I will make another list for $1000 and above in a day, or two.