Consider using a Buck/LDO combo for +5V
Using a DC/DC converter followed by a low-noise LDO would sort out the power dissipation issues in the 5V PSU, ensuring a very low noise level.
We successfully used LMZ31704 DC/DC (overkill in this case, 4 Amps) followed by a low noise LDO (TPS7A8901 or TPS7A4701) to power an ultra-low jitter RF distribution system (see https://ohwr.org/project/ertm15-llrf-wr/).