The Sony 5400ES only outputs multi channel SACD via HDMI. There are many receivers which will convert to analog. Some really nice ones are out there for about $500. I however don't want one, I just want what I'd call an HDMI DAC to convert DSD to multi channel analog which I can send to analog multi channel pre amp.
The Oppo BD players have an HDMI input, and can be used purely for the function you mention. They also have BD drives in them, and can play SACDs and DVD-Audio discs themselves, but if you want to use your Sony, you can do so and just use the HDMI input on the Oppo.
Due to the economy of scale, most likely, if a thing that does just what you want (and nothing more) exists, it will likely cost far more than the Oppo. This is not entirely dissimilar from comparing receivers with preamp/processors, as typically, the receiver will cost less for equal or better performance than just a preamp processor, so basically, the manufacturer is paying you to take the built-in amplification. The same idea applies here; Oppo is paying you to take the BD/DVD/CD/SACD/DVD-Audio drive along with the conversion from HDMI SACD to multichannel analog.
Why would you want to pay more to get less?