Yes, you can use a conventional center channel for SACD and DVD-A. While it may not be the absolute optimum but it would sound OK. A center channel speaker derived from the drivers similar to those in the arrays would be a closer tonal match.

I'm more of a stereo kind of guy myself vs. multichannel music but to each his own. Multichannel video disks are OK for movies but I'm not happy even with music DVDs--especially when in some mixes the sound comes from a different direction vs. where the video shows a performer at a different location. By the way, I've had Yamaha DSP (7.1 channels) surround sound in some form since 1990. Dolby Digital and DTS formats don't do it for me except for movies. Hopefully, multichannel SACD and DVD-A are better than DVDs in terms of audio.

On the text in my reply: I think I said things correctly. I'm saying that the best ultimate situation would be to use arrays for the fronts and rears (2 pairs) and two subs. What I'm suggesting in the last paragraph is to start by building one pair of arrays and trying that for a while and ultimately build out the rest of the system. I suggest also that the Linus 3 is superior enough (vs. the Linus 2) that the Linus 3 that it would be my preference. Either the Linus 2 or Linus 3 should easily trump the DefTechs in your room. One thought is to build the Linus 3 for the fronts and the Linus 2 for the rears. Best though would be all Linus 3's.

On the subs if you go with the Linus 3 I would work that issue with Rick Craig at Selah Audio. I like the Peerless XXLS in either the 10 or 12" range. You might go to a 15" set if you are a real basshead and can tolerate larger cabinets. My preference for music is a sealed box sub but that would not give you the whack of a vented sub for movies.

On the the 135watt Yamaha RX-V2600 receiver: It should drive the arrays and the rest of the surround sound system just fine. For the subs I suggest separate plate amps for each one. Usually, you'll need more power for the subs than your receiver can supply. Plate amps that have parametric adjustments would be nice to allow some correction for room modes in your space.

That should do it.

Jim