Its always interesting when people start talking speed with regards to HDs...
Doing some rough calcs...
For each mono track, 24 bit, 48KHz, the bitrate is going to be 1,152 Kbps. So filesize is 144 Kb per second, per channel written to disk.
For 32 tracks...
144kb x 32 tracks = 4608Kb/s, so in Mb, 4.5Mb/s
So realistically, any HD will do at those kind of write speeds. Of course, with a magnetic drive, you'd hope that you've got the disk defragged for recording. Of course SSD doesn't suffer with fragmentation.
So when I say any HD will do... they will... as pretty much any 5400rpm HD will handle write speeds of way more than 4.5Mb/s.
In short, the hard disk is not going to be the issue when tracking. Editing however, you'll probably appreciate the faster disk speed.
If you suffer problems whilst recording - especially long sessions - it's probably down to your choice of daw, or buffer on your audio device.
In short, processor for recording and then RAM for are king.
For clarification though - SSD for at least your system disk is going to make your system feel a lot lot lot more responsive.