Everyone has different opinions, and definitely different hearing capability.
With that said, I ABx Ref1 with Logitech Transport with no upgrade at all. and I found the difference to be 'minimal' at best.
The source was network streamed for Logitech Transporter and I used the m2Tech hiface as well as using Transporter as a Source (which should have a very good jitter performance).
In the end, the difference is pretty much 'none' to MY ears. If I were to buy a new DAC, I don't mind buying Transporter nor Ref1.
What I am getting at is, the jitter performance is pretty much non-issue with reclocking dsp-1 inside the Ref1. It's mostly the power supply and the CHIP used inside the DAC.
If you can hear the jitter difference between 90ps and 200 ps, it's totally different ballgame, I suppose.