A multi-channel amp is all that is required as long as you don't want any auto-EQ circuitry. The Oppos are exceptionally good units and running them direct into an amp sounds very, very good...
For that use you want the Oppo 105 with its superior analog output. You cannot use an analog source such as a phono stage, because the Oppos accept only digital input. An Oppo 105 directly into an amp should sound very good, if it satisfies your input needs.
I don't know what your budget is, but if your budget permits you may want to investigate the Parasound Halo A31 (retail $3000). The A31 is a rarity in that it's designed specifically to be a three channel amp as opposed to multi-channel amps that are also concerned with surround and/or back channels.
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