You could look for some used Matrix speakers on Audiogon or Ebay - if you are looking for a perfect timbre match. Otherwise N805/1NT for bookshelf or SCM1/SNT for on-wall (from the Nautilus/CDM lines respectively). The new 700 series is also available.
IMO, if your use is HT and 2-channel you don't need to have the same speakers all around. On the other hand, if you listen to hi-res multichannel music you may want the same speakers all around.
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