The rule of thumb is that there is no rule of thumb. You have to experiment and see which way you like it best, not me or anyone else!!!!
Kind of a dumb question...
If you own two pairs of ICs that are not of the same quality, is there a rule of thumb as to which one should be used between the source (CD player) and preamp versus between the preamp and amp? I know someone out there is going to tell me to experiment and come to my own conclusion, and I'll do that. But I'm curious to know if there's a general rule of thumb.