The concept of timbre matching is way overstated IMO and i can't say i've even seen as many conversations about it in the past couple of years.
You "might" notice a difference between surrounds that are a markedly different design/size (e.g. a direct radiating vs. a quad design), but noticing a difference in timbre between fronts and surrounds in general?
Unlikely.
The QS8s are a fantastic surround speaker and even though i may hunt for something different for my mains, i won't be giving up my QS8s. Of a few other companies that had similar designs (bipole or quadpole), Axioms are by far much less expensive and are solid little units. Very easy to place.
