I have the D-40r which are similar to the D-48. I ran them for many years with Quicksilver V-4 (tube) amplifiers. They sounded great, but they now sound better (IMO) with an Aesthetix Atlas (hybrid) amplifier. My experience was that they needed more bottom end control and grip.
If you want to look my system is posted here on Audiogon.
If you want to look my system is posted here on Audiogon.