I have owned an Audio-gd PCM1704 DAC for a few years now and have put some of the best DAC's I could get my hands on against it. The Audio-gd always wins. I tried his ref1 and ref 7.1 but always felt something missing compared to the older models. I believe the issue to be jitter from the FPGA integration. I found a DAC from Rockna called an RD-30, it uses the Xilinx Spartan6xling FPGA but the DAC designer worked Xilinx's engineer to get the most out of the chip including a claimed synchronous pll with the CCHD-575 clock. It also has an asynch usb input where the CCHD-575 is switched to master clock. If the claims are true this could be a real nice alternative to the Audio-GD products. They also come an I/V stage with current steering NFB free topology. I went a head and ordered one when I learned the oversampling filters can be chosen from 4 different types including an apodizing filter.
Rockna has a good reputation in Europe with multi-thousand dollar DAC's and this RD30 although requires a minor amount of assembly looks on paper to be a real nice alternative to the Audio-gd PCM1704 DAC which are truley nice but I am hoping that this RD30 will be a final answer to a true hirez PCM1704 DAC with less jitter than the DSP-1 and a better analog stage than the ACSS modules.
Regardless its nice to finally have a modern alternative, hopefully the DAC will get here before Christmas and I can post some comparisons to the Audio-gd PCM1704 DAC's if folks are interested.