I really dont know much about Equinox, but I am a K2500 user. The internal orchestral sounds are great and realistic sounding. There are also a vast library of sounds available for the Kurzweil on floppy and CD-Rom. The Kurzweil is not something you will outgrow. The only minor setback may be the issue with polyphony. I believe Equinox has 64 note polyphony, the K2500 has 48. But one needs to understand how the K synths work when it comes to layering keymaps. For example, one layer of strings on a K sounds great, you may not have to use multi-layering to get a great sound. You could eat up polyphony by using 3 layers of strings for example.