I think you start from the wrong approach, looking into hardware first...
The most important question you should start with is : WHAT IS THE PURPOSE of that LN node?
There are many ways, modes, types of LN nodes and each one have its own type of setup and hardware.
You have:
  • learning nodes, that can be a shity RPi
  • developing nodes, that also can be a RPi or a could node (temporary)
  • routing node, if you want serious business, run a serious server not a shity RPi
  • playing around, but stable node, use a NUC with strong hardware
  • private node, personal use - you don't really need a desktop machine, nowadays you have full mobile nodes, enough for running your private LN payments.