I think the P3 is an excellent DAC. I have not heard it with the T3, but I use it with the sony xa 777es as transport. I use the meridian 518 for anti jitter/noise shaping and it sound just extraoridinary. On the TELARC SAMPLER 2, in which the sources were recorded with DSD, analog or hi-rez PCM, the P3 sounds as good as the two channel sacd layer. The sacd has better organic flow, but the P3 has better bass, detail and slam. They are so close, it is not a really a question to me if one or the other is better, just if on a particular recording one or the other might be preferable with sacd or pcm.
The SF MK3 is also good, but not as spacious sounding as the P3 on redbook sources. However, it is incredibly good on DAD with 96/24 sources. The 96/24 DAD sound has great solidity, body, and tonal accuracy compared to the somewhat lighter sounding sacd.
The P3 is much better sounding than the redbook dac built in to the xa 777es. I don't think the built in dac of the xa 777es, even with mods, could ever compete with the P3 i.e. the P3 has bulletproof power supply and incredible output stage as well as the still state of the art ultra analog dac's. The built in dac of the xa 777es seems to have the sound compressed into a fish eye oval compared to the P3, which sounds limitlessly spacious and open.