any science to mix and match speakers for HT?


Ardent two channel audiophile wants to create entry-level home theatre. I wanted to create 5.1 system using my 13 year old Thiel 1.5s as front R+L and wanted to know if anyone thinks it is very risky ( for poor final sound) to just buy any decent used mid level audiophile quality center and rear speakers? I already have a decent mid level velodyne sub. Thiel has a rather high end center that is above my budget so I was looking at others.
thanks for advice
idguy
Have you tried just using your 1.5s without a center channel speaker and just adding surrounds? Unless you have people sitting well off axis to the sweet spot you may find you might not even need a center channel speaker and possibly avoid whole the matching hassle altogether. I did this for years and never missed having a center channel speaker. On the other hand, I've heard lots of 5.1 systems even with matching centers that sounded like crap for dialogue. Just another (and considerably cheaper) option fwiw.
You should be able to find some 1.2's or so for under $400. Buy 2, use 1 and put 1 away somewhere? That should do the trick? You really need the same voicing across the front 3 speakers. Rears don't matter as much.