My first question would be: How big is the SSD you purchased? That info would give an idea of the most useful use for it. IMO it's no use putting a, say, 125 Gb SSD for audio, because it would be filled up so quickly.
Then again, if it's 500 Gb, it would be hard to decide, as that would be quite much for a system disc. Then you fill it with something else aside, and are soon in the situation that you need to move stuff from the system disc or move the OS etc.
Due to the price of SSDs, and for other practical reasons, I would use a smallish SSD as system disc like so many do.