When I had the original Mhdt Paradisea DAC my two favorite tubes were the Bendix 2C51 and the GE 5 Star 5670. The Bendix is nicely detailed with great imaging and soundstage. The 5 Star is a close second and was a very good value at the time. The 5 Star did not impress me at first, but with some burn in became more coherent and much better sounding. Some people like the WE 396a, but I found it to be a bit fat in the lower mid-range and bass. The D getter WE 369a tubes seem to be considered a bit better than the later O getter tubes.