My first-ever project! Please help

[Ric_LV]

This will be my first-ever project, a splitter/mixer. It shouldn't be very difficult to build, but still I don't know how. How sensitive knobs to use, how many ohms to use, what kind of power supply to use, etc. I'm totally new to all this.

The splitter/mixer must have 2 XLR stereo inputs and 2 RCA stereo inputs. Each stereo line must have it's own volume knob and on/off switch. Then all 4 stereo input lines join into one main stereo line. This main line also have it's own knob. Which will be the main volume knob. The main stereo line then splits in 4 stereo output lines: 3 XLR and 1 RCA. Each output line must have all 4 inputs' signals with no power loss. That might be the trickiest part. By my view, all of this should be mounted in a 2U rackmount box (is it possible to get one?). There is also a drawing attached to this post, so it's more clearer. Sorry, if it looks like drawn by a 7 year old. Don't have a experience in drawing schemes.

Why do I need this?
There are four rooms in my house and there are often parties there. I actually rent my house for parties. I want to have a better control over the sound in all four rooms. Besides, this splitter/mixer will also work as a preamplifier.

[Ric_LV]

Here's a quick scetch of the splitter/mixer

[cunningham]

Just buy one and save lots of trouble.