I had a similar situation when I bought my emu card. It has 1/4 in jacks and all my stuff was 1/8 in jacks.

If you get the 1/4 to rca converters, it should all work out. In my system, the 1/4 outputs can be combined to a single stereo, which I then split into powered speakers and headphones. The output is sufficient to drive the headphones. It is hokey, but it works.