When is a mismatched center OK?

Hi all, 

I'm going to go listen to some speakers in the next 30 days and need your advice.  My goal is to improve my 2 channel experience but I have to be cognizant of HT also.... and my primary problem is as follows:  For many of the speakers I like the center channel is freaking huge.  (Looking at you Paradigm Persona!)  I don't have room for the standalone style center.  I could reconfigure my rack if needed but like the way mine sits today.   I could shop down market a bit where the centers are more reasonably sized (Founders instead of Persona,) and likely still be pretty happy.  

I recognize that ideally you don't want a mismatch, but.....What I'm wondering is if you stay within the same family (Example:  Focal Sopra 2 with Aria center) , would your timbre match be solid enough to get by or would you create a potentially glaring mismatch?  

Any first hand examples appreciated.  

Thanks, 

Eric