Centre speakers from Castle, JMLab, ProAc, Thiel, Vandersteen and Totem (speficically Model 1) are tested and reviewed in UHF (Ultra High Fidelity) magazine No. 67. The back issue only costs $4.99.
The overall panel of listeners found the Model Ones very good but ultimately trailing behind Thiel, JMLab and ProAc.
Here's the summary:
Most Liked: Surprising body, plenty of dynamics
Least Liked: A somewhat elevated top end, occasional coloration.
Good luck.