Let me try and explain what I have now-
Let's start with audio.
Going into my computer is the Fast Track Pro. Plugged into each of the FTPs audio inputs is an adapter that accepts two 1/4' mono inputs and converts them into a single mono 1/4' output.

from each of those runs two 'guitar' 1/4 cables. for example, lets take the FTPs left input; from the adapter runs two cables, one into one synths left output, the other to another synths left output. Then from the FTPs right input, the adapter routes two cables to two synths right outputs.
With this setup, if I use two synths at the same time, both have their output diminished do to the nature of the cabling. So let's say I'm using the X50 with no volume as a MIDI controller for the R3; the R3s output will be cut in half simply because the X50 is on, unless I unplug the audio cables from the X50.
If I want to use my microphone, I need to unplug the left audio inputs entirely, plug in my XLR cable, and then turn on phantom power and boost the input gain.
Now for MIDI; I have one standard MIDI cable. If I want to play my slim phatty with a keyboard, I connect it from my X50 or R3 to the SP. If I want to sequence a line through Logic, I then have to reroute the MIDI cable so that one end is in my FTP and the other is in my synth of choice.
This is all really inconvenient for me, so I'm trying to figure out how I could do the following.
The first is, I want to have all my keyboards plugged into a mixer of sorts where I can either choose which keyboards audio to output to my computer, or mix each keyboard into my computer. So basically I'd have instrument cables from every single one of synths running into the mixer, and I could toggle either by button or by mixing levels which synth goes on to my computer and Logic. Also, it should be able to accept an XLR input and provide phantom power.
It doesn't matter to me if the mixer outputs directly to Logic via USB/Firewire, or if it sends out stereo or L/R Mono audios which then pass through the FTP first which then forwards it to Logic.
For midi, I'd again like MIDI cables running to all of my synths, and then have the ability to choose a controller (be it one of my synths, Logic's output through my Fast Track Pro, or a master MIDI keyboard which I may buy in the future) and route it to one of the synths individually as a receiver.
Any ideas on products to do these things, or, if it exists, a product that could handle both the MIDI and Audio in the way I want to?
Thanks ^^