There's a certain amount of apples and oranges confusion here, I think. The number of simultaneous tracks in a DAW is not the same as the number of simultaneous inputs. The number of simultaneous tracks is determined by a few factors:
- The amount of available RAM. You always want to avoid forcing the DAW to use paging, i.e. swapping memory to disk because an insufficient amount of RAM is available.
- The amount of VSTs versus audio tracks or MIDI tracks that control external devices. VSTs can take up a significant amount of memory and can tax CPU resources.
- Where in the chain effects are applied, and what the effects are. Applying reverb to 10 tracks individually demands more from the CPU than directing the 10 tracks to a single bus and applying reverb to the bus. Some effects are more CPU-intensive than others.
- The speed of the CPU, the number of cores, whether the CPU is hyperthreaded, how hyperthreading is implemented by the operating system and how hyperthreading is implemented by the DAW. This is a much longer topic than can be addressed in summary fashion. Suffice to say that faster CPUs are better, multi-core processors are better, but only if the DAW supports them, and hyperthreading may be better, but can also degrade performance, depending on how it's implemented by the OS and the DAW.
I have projects that include over 100 tracks. I find that available memory, CPU speed and ASIO buffering have the most effect on these projects. I have two computers that I use for music -- one for composing and creating, the other for mixing and mastering. Both run the same DAWs (Sonar X2, and, though not truly DAWs, Audition 3.0 and CS6). The composition computer has a 4-core AMD CPU, an SSD drive (used only for program, project storage and as a scratch disk) and is now equipped with 8 gig of RAM. I had to bump it up from 4 gig of RAM because Sonar was choking on too many instances of a specific VST I needed for a specific project. I rarely exceed 20 or 25 tracks on this machine. The mixing and mastering computer has a 4-core Intel chip, an SSD drive (used only for program storage and as a scratch disk), a 3-TB RAID 5 array (used for audio storage) and 8 gig of RAM. I've had no need yet to bump up RAM. This is the machine that mixes my 100+ track projects, which are also long works -- between 7 and 8 minutes. Note, however, that, by the time I'm working with these projects on this computer, I am dealing solely with audio clips, to which I apply EQ, reverb, pitch correction, etc.
I also have a laptop that I use primarily for location recording and as a backup to my primary systems. It has a 4-core, hyperthreaded Intel CPU, an SSD and 16 gig of RAM. It can handle absolutely anything that I throw at it.
An 8 core 4 GHz CPU sounds like far more than you would ever need, though the price is certainly good. 16 gig of RAM is almost certainly more than you need, but RAM is relatively cheap and it never hurts to have more RAM than you need. The kind of recording that you've described is, more or less, what I do -- I've been using
Addictive drums, split to 16 tracks, a dozen or so VSTs and around 8 tracks for vocals, though I find it easier to transfer those tracks from Sonar to Audition for mixing, where I will frequently split clips either for mixing purposes or for correction.