I did a little test, and this appears to be consuming lots of memory, so I don't think you are going to be able to do it with your configuration.
Vixen startup - 17MB memory
2 512 channel ~3 minute songs at 25ms - 46MB
3 512 channel ~3 minute songs at 25ms - 113MB
4 512 channel ~3 minute songs at 25ms - 152MB
I'm not sure why it is not a more linear growth pattern, but based on that sample you could need greater than 760MB of contiguous memory (if it became a more linear growth curve).
It also consumes significantly more memory if you have the sequences themselves open when you try to manage the schedule.
Same sequences with a 50ms event duration consumed less than half the memory (as expected).
That said, you said it was working....If you think it is a bad sequence that is causing it move 10 of them out and try to manage the program to divide and conquer. If you want to zip them up I'd be happy to try and open them on my PC to try and rule your machine out.