Tubes can be noisy buggers, and for this reason some people prefer keeping tubes away from the low-level signals originating from source components. This would favor those who support using a ss preamp and tube amp. I'm not saying this is right or wrong, just that it is one rationale for going one way over the other, and results will obviously vary from system to system and component to component. Like most things audio, this is one of those areas where you'll likely have to try some combos yourself to come to your own conclusions, but hey, isn't that half the fun? Best of luck.
Tim
Tim