is2e or is2 transport.. what is available?

In addition to SF, Camelot, and Muse, look for a used Audio Alchemy DDSPro. Great machine.

I think the I2S and I2Se have different connectors. I'm using an ST connection out of my transport fed into an Assembledge D2D-1 upsampler/jitter reduction unit. The D2D-1 has the same I2Se output as the Sonic Frontiers input. Even my $200 DVD player sounds good as a transport into this set-up.
Suggest you look into a D2D-1.

I've been running an EAD T8000 Universal Disc Transport into my SFD2 for 5 or six years. It sounds splendid and when combined with a great aes/ebu balanced datalink, some Amperex NOS tubes in the output stage, and a balanced pre on its outputs has managed to fend off all challengers in my listening room. Amongst those challengers, I would include the SFD2-seriesII. The early HDCD filters were not a step forward on anything but HDCD encoded material.

About a year ago (when it first became available) I had the Series III update performed on my DAC this was packaged with the D2D-1. The upgrade to the DAC was very worthwhile. Transparency improved, as did soundstaging, and along with this came a significant reduction in grain (I had been only subtly aware of this grain in the prior version of the DAC. Its later absence seemed quite obvious though...) In my experience the D2D-1 is not always a welcome interface between the Transport and DAC. On bad transfers the up-sampler is a positive addition, removing the rough edges of poorly mastered material. But, with well-recorded music, the D2D-1 was a bit too warm and fuzzy.

The T-8000 was and is still a great Transport. I've always used a great digital data-link, only recently switching from an XLO Signature to an Orchid- both in the AES/EBU balanced versions. Finally, I have paid a lot of attention to details of power, proper grounding, and vibration isolation. Perhaps If you are less carefull with all of these issues, the D2D-1 would provide a more positive contribution making up for short comings in these areas to some extent. As things stand in my system, I would strongly recomend the Series III update to any SFD2 owner but as for the upsampler... Borrow one and have a listen before you buy.