A faster hard drive (read write speeds) will impact how many tracks you can record simultaneously as well as how fast the system boots and apps load
RAM will affect how well sample based softsynths and such work (more RAM = more space to store samples and less need to pull direct from HDD which is a slower call, Faster RAM means it can pull the samples fasterl)
CPU how many complex VST/VSTi calculations can be handled at the same time.
None of these will affect quality of recorded sound, as mentioned earlier this is a factor of the basic inherent quality of the actual live sound (musicianship, instrument quality, room treatment), Mic choice, Mic placement, Preamp choice, converters. If you are looking at better quality of sound this is where you need to focus not on the computer.
In much the same way that a word document will not be any better written or more attrictive on a faster HDD, audio will be no different on a 10 year old EDI 5400 rpm drive than it will be on a brand new, hyperfast solid state drive from intel. The HDD is just the receptical for the recording once it has been converted in zeroes and ones by the outboard gear. How fast it spins reads and writes do not effect those ones and zeroes in the slightest (except possibly a placebo effect because one has just upgraded the machine so one is looking for a change)