Hi,
I actually have that exact setup right now. (De Capos up front and Dulcets for the rear, in a 4.1 configuration)
I love the setup, and haven't noticed any issues with tonal differences between the speakers.
I am using a Linar 10 (5.1 Integrated amplifier) to combine two-channel with home theatre, and for the first time, I am happy with the sound of both sources of entertainment.
I wouldn't hesitate to recommend the De Capos and Dulcets in a 4.1 configuration. Reference 3A does have a centre channel version of both the De Capo and the Dulcet, but I am satisfied with the 4.1 setup for now.
Cheers,
Derek Stewart