I know nothing about the hardware modifications, they do sound interesting, though I'm quite happy with the Touch as an untouched (haha, eh, sorry) digital source.
I did experiment with the software hack, and found the difference insignificant.
I also had a dedicated power supply, a Russ Andrews Squeezepack for a while; again I found the difference with the sock power supply insignificant.
However, we all have different ears and different systems, and the sensitivity of the DAC for jitter (and perhaps RFI and EMF?) no doubt plays an important role in how big the differences will be.
Strangely I found the difference the digital cable made remarkable, a Digiflex cable sounding bland a Bolder cable sounding clear but slightly too bright and an Oyaide sounding smooth, the golden midway (that was with my former DAC, ther Audio-GD Ref5DSP). I can't explain why.
I use wireless on the system listed in my sig; wireless might be less good because the wireless receptor has to be on, but the idea of a PC close to the Touch and DAC somehow doesn't feel right to me.
If the PC is placed near the audio system a digital interface sure makes sense to me, as shielded cables and power filters would do. If you use USB I think the need for an interface would grow.
Please note all these are assumptions from me and I've no experience in practice