Everything is important
Getting rid of the switching power supply would be the most important thing to get the most out of the Logitech Touch.
The mods to the Touch do offer very good bang for the buck. There are some folks here that are very happy to just use an analog modded Touch with BOLDER PS into their integrated amps.
I happen to prefer the sound of the digital output of the modded Touch into a modded Eastern Electric DAC. There is a long thread here about the EE DAC and the mods I have come up with for it. There are also a few comments comparing the modded unit to the stock one and some other DACS.
Here is the long thread about the development of the mods. MusicMike had a chance to listen to it compared to his stock EE DAC and he should be writing up a review on it for stereomojo.com.
There are lots of threads, and reviews about the EE DAC. In stock form, I think it is one of the best sounding DACs for the money available today. You can have lots of fun with tube rolling 12AU7s.
With the mods, the DAC could be one of the best sounding DACs for under $5,000.00