Recently I've been searching for a decent, but not too expensive compressor for vocals. From a bunch of research, I was able to deduce that the Aphex 651 or 661 would be better for vocals than a DBX 160a. Now, the question is which Aphex compressor should I go with? The 651 or the 661. The the only difference between them is apparently the tube output stage added in the 661, though both are extremely transparent from what I hear. The preamp that will be used is a Blue Robbie, which is also has a tube stage, but is quite transparent. Could anyone shed light on the benefit and/or lack thereof of having two pieces of gear in the same chain with tube circuits? Since both the preamp and compressor are said to be transparent, is it even an issue? Which comp would you recommend? Thanks!