I also use JRiver and it's the best media player for a HTPC.
You could also just use MPC-HC with LAV Filters and if you have a strong graphics card madVR. MPC-HC with LAV will play almost anything and will convert almost anything to PCM problem free. The only issue you will have is with DTSMA. For that you will need to get an additional .dll.
JRiver, LAV Filters and madVR will give you the best playback quality possible on a HTPC. With properly ripped blurays it will even beat most stand-alone players out there. If you need more details I can help.
