What non-upsampling dac betters the DCS stack?

Zanden, AudioNote...
the Zanden, according to avant-garde
I've heard of one person who dumped his DCS for a Twin Dac Plus with a computer for a source. I just got my Twin Dac, so no opinion yet...using iBook as a source
The only combo that really betters the DCS stuff is the Barclay X-1 transport combined with the big bad Boulder DAC. I had the pleasure to listen at my dealers place to several state of the art digital playback systems (Wadia, MBL, DCS, Accuphase, Spectral). The Barclay Boulder combo has to be regarded (my dealers view and clearly mine) to be the best digital combo around.
What's a Twin Dac?