2x TRS 1/4" to RCA cable (both male ends)

from what i know, and i might be wrong, but i own the emu0404usb and the 1/4 outputs are mono outputs, which is why they are specified left and right. so you would want two mono plugs (TS, not TRS) going to two RCA plugs. And if you wanted to plug headphones directly into your emu, then you would need two mono 1/4" plugs going into a stereo (TRS) female 1/4" or mini, depending on what plug your headphones have. 

right.. so TS will either only give u left side or right side signal, whereas stereo (TRS) will give you both left and right

With pro-audio style things a TRS connection is for balanced and a TS connection is for unbalanced.

Usually the connections on pro gear can be converted from balanced to unbalanced by using a simple adapter.  For example, to convert from TRS to unbalanced you'd just plug in a TS cable or use a TS to RCA adapter (Radio Shack also sells a similar adapter).  There are also XLR to RCA adapters for equipment that use XLR connections instead of TRS.

The thing to be aware of is that balanced connections are at +4dB while unbalanced connections are at -10dB.  So you need to adjust or compensate for the different levels of balanced vs. unbalanced.  I took a quick look at the E-MU site and the 1212M has software settings for -10dB or +4dB levels on the outputs and inputs.

So in your case you'd use a TS to RCA adapter, set the level on the output to -10dB in the driver software settings, and use whatever RCA cable you want.

Doing balanced interconnections (TRS or XLR) is generally better but not necessary.  If you have unbalanced equipment in the chain, like a pre-amp or whatever, you lose some of the benefits of doing the balanced interconects.  In home use where you're mixing consumer gear with pro gear the balanced interconnects don't make as much sense. If you have to do a really long cable run then do it balanced, but for regular home use with regular home use cable runs it isn't so necessary to bother with balanced.  People have big buck home stereo systems where everything is unbalanced (regular RCA cables).

I have a mix of pro and consumer gear.  My interconnections are all unbalanced except for the cables from the monitor control to the monitors.  I had the necessary TRS to TRS cables on hand so made that short cable run balanced for the heck of it.

So don't worry about it.  Do everything unbalanced if it's more convenient that way.

I ran into this issue not long ago at all. I bought speakers which only had TS/TRS and XLR inputs, so I was unsure to get RCA to TS or RCA to TRS. Since each speaker is individually powered, TRS would be useless, so I just went with RCA M to TS M.