Chuck,
I'm also a JSE Infinite Slope fan and recently complete my speaker system, (4) JSE Model .6s which are the 2-way 8" woofer & 1" tweeter in a vented cabinet, by adding the JSE Model .5 as the center channel speaker. The Model .5 has the same woofer, tweeter, and infinite slope crossover as the Model .6 only in a slightly smaller cabinet. Perfect size for center channel. I simply laid this speaker on it's side and it sounds wonderful. I have a spare Model .5 left over that might suit your needs. You could check with John Sollecito at Source Loudspeakers and confirm that the Model .5 woofer & tweeter would blend well with your Model 1s. Feel free to send me a PM.
Ward