If you go from 44.1K to 176 you are actually adding new data points between the original data points. That is usually done with a curve based on the surrounding points. In fact many DACs have done that for years. Some people like the sound of the additional points and some do not. But there is more to upsampling than simply adding zeros.
If you are going to upsample 44K files, you should probably use 176 rather than 192, since you maintain the original data points. The math is easier and put less strain on the CPU, which can be important if you are upsampling in real time. And upsample 96K to 192.
You can do the conversion on the fly by simple settings in DSP studio. Just set 44K to upscale to 176 and 96 to 192. No need to convert the files, at least when you are evaluating the sound difference. It is a pretty easy experiment. Give it a try.
I just looked at your pre-amp/DAC and it is already upscaling it to 24bit/384KHz, so doing any upsampling in MC in unnecessary. According the the Cambridge Azur webpage on your 851c,
"All incoming audio data, such as CD quality 16-bit/44.1kHz, is upsampled to 24-bit/384kHz using a high-end 32-bit Analog Devices DSP (Digital Signal Processor). "Polynomial Curve Fitting Interpolation" provides a much more accurate upsampled audio soundwave than traditional upsampling processes. And a unique timing system buffers audio data to almost eradicate digital jitter. Vital – as jitter, common in digital audio devices, loses vital detail, often leaving digital audio sounding flat and lifeless."
The increase in quality you hear in your 96KHz and 192KHz files is probably due both the re-mastering and the increased sample rate.
Seems like with your 851c, upsampling the data stream is probably no going to add anything, but, hey, give it a try.