You are welcome, Kaushik
See Sneetch already explained phantom center - thanks, Sneetch. Again, if you are mostly music, you may not even need a center and just get by with the "phantom" center when it's movie time. Alternately, if you are set on a center, what about under the mantle, perhaps angled up slightly if needed, mounted either to the brick or to the wood (eg, maybe an "l" bracket)? Upcoming Luna Duo might work (dimensions in the Luna thread post 972).
I've not heard the Towers with dome tweeter so can't comment on this versus the RAAL. Suggest you call Dina or Dave at Ascend and see what they recommend based on the type of music you listen to. I listen to anything from classical to jazz to classic rock to heavy metal, and all sound excellent to me with the RAAL. Speakers I had before moving to the S2s were Def Tech Monitors with Al dome tweeter. They could be fatiguing over a listening session.