Least Expensive Route

So lets get this clear before people start jumping on this thread bashing me and saying I hate when people buy gear and then dont know how to use it. I grew up in a drumming household and have recently turned to the amazing side of DJing. Recently I have been wanting to start producing some of my own tracks. The wonderfull fiance that I have went out and purchased me a M-Audio Venom Synth along with some TRS to XLR cables. (the ones the service rep told her I needed to hook up to my KRK's) Well those cables work just fine and dandy but cant be plugged in when using my Novation Twitch thorough my KRK's. I have the feeling that im going to have to get a mixer of some sort. I didnt know if there was a cheaper way to go possibly using either interface from the twitch or venom to allow both to be played at the same time. Like I said im new to producing and with being a drummer never really had to run cables other then to a mixer. Any input would help as im looking to expand my knowledge. Thanks

Also if a mixer is the only route i'm up for unput on what people feel would be the best mixer to get the job done without a hefty price tag. I can figure this all out myself I just like the input from users who have way more knowledge then I do.