I have found that external DAC's are the best option for me, as the technology in those has improved over the years, have had three of them to date, don't use the DAC built into my pre-amp. For the last 14 months have immensely enjoyed my PS Audio DirectStream DAC.
I have a C50, find that it warms up very quickly and to me, sounds great. One of my audio buddies is trying to get me to upgrade to a C2500. Over three decades ago I worked in the high end audio business and found that tube equipment deteriorated, so after several months, swapping out the tubes on an amp-preamp setup dramatically improved the sound. Since then I've steered away from tube equipment.
I have a C50, find that it warms up very quickly and to me, sounds great. One of my audio buddies is trying to get me to upgrade to a C2500. Over three decades ago I worked in the high end audio business and found that tube equipment deteriorated, so after several months, swapping out the tubes on an amp-preamp setup dramatically improved the sound. Since then I've steered away from tube equipment.