IMHO the quality of recording/playback of several tracks will not be so much affected by the drive maybe unless its a sample rate well above 48k ...just my experience.
Sample vsts and so forth (where near instant buffering of a gigabyte and such amounts of data is needed) are where the SSD is most helpful.
For recording/playback of a few tracks there is just not that much speed necessary for the read/write as compared to the need for audio card accuracy.
On the other hand if the system does not have an extremely accurate clocking mechanism to precisely render the A/D, that, and not the drives, will be my big concern. I haven't often played back more than six or eight stereo tracks at once though, and I guess this is a big factor (my workflo involves using a lot of plugins, freezing and combining as I go). I avoid using Guitar Center -grade soundcards and even my usb drive-recorded/played back stuff sounds clear and accurately reproduced, since the clocking by the soundcard is pristine.
That's assuming the goal is recording and playback quality and power.
For running plugins, may be that the SSD frees up the cpu cores tho, so that would be the other reason I might using them.
For plugin performance I am considering using a networked solution to allow for plugin operations on multiple machines..
