whatsinaname
Innovator

The image above, produced using my l33t MS Paint skills, is my current audio setup. I am looking to improve it by replacing my DAC and Phono stage. (Speakers are fairly new and I quite like them. Not looking to make any changes there. The same situation with the record player as well.)
I am looking for suggestions on how to set this up. (Not looking for individual component suggestions, I can decide on budget and specifics later).
Basically, I want to be able to pipe audio from my computer and from the record player at the same time to the same set of speakers. No source selection involved. My current setup does do this, but my computer has to be turned on for me to play music from my record player. Is there a way to get around this? What components will I need?
A receiver? Will that take two sources and send them to the same output?
Will I need a separate DAC + phono stage + Mixer?
Is there any one device that will do this?
My speakers are active monitors, so I don't think I specifically need an amp.
Any and all suggestions are welcome.
If my components have any bearing on what the answer would be, they are
Record player - Rega Planar II
Phono Stage - Some cheapo one I had bought just to get my setup up and running. This one, to be exact.
On-board sound card - Realtek ALC889A
USB DAC - nuForce uDAC 2
Speakers - Yamaha HS50m