the most obvious difference is that the sax has variable gain and the psp2 is fixed. I ran a psp2 for a while and it was very nice indeed. I'm sorry I sold it. It was light years ahead of the mp2 it replaced. The psp2 has a nice tight low end that is fat but not floppy. As others have said it reminds me of a mini Ga brick. I ran mine with an oade modsbm1 and the results were very good.