Sample rate conversion and audio quality question

[Beck]

... but I want to record the reamp'd guitar parts at 44.1 to save processing power, otherwise the system's going to start choking once I get a bunch of other parts recorded.

I'm more curious as to why your system is choking on 24/48, but not 16/44.1. Often questions like these reveal another problem you should be addressing that would make the original question unnecessary. Have you tweaked and tuned your PC hardware and OS for recording, and do you understand that step and and how crucial it is? I would examine your system first, make sure its running optimally and then address any further issues if it doesn't fix them. I find the vast majority of recordists today are NOT running PC systems optimized for DAW use... and that is the cause of most other problems.