The A-48S is a very capable amplifier - and hardly stressed by speakers that are as sensitive as 105 dB.
As I mentioned before I heard a significant improvement going from an older C-2450 pre-amp to the C-2900 with my A-48. The C-2300 replaced the C-2450, and I have not heard it but I imagine the C-2900 is a step up.
Accuphase matches it's pre-amps and amps as follows:
C-2300 + A48
C-2900 + A-80
C-3900 + A-300
Your DAC might be the first area for improvement. The DC-37 was introduced in 2014, and it was apparently based on the DP-720 SACD player introduced in 2013. The DP-720 was replaced by the DP-750 in 2018 which was then replaced by the DP-770 in 2023 or 2024. The DC-37 was never replaced as a stand-alone DAC, but it is several generations behind and is now in the 'product museum' - meaning it was discontinued. It was in essence replaced by the various SACD players listed above.
The only other stand alone DAC produced was the special anniversary DC-1000 introduced in 2021. I have not heard it but from perusing reviews it sounds like it is very special.
Apparently listening to CDs in Japan is still more popular than streaming, which is why companies like Accuphase, Luxman, and Esoteric are still producing new and improved SACD/CD players. The new DP-770 SACD player would be their newest DAC.