I had this same problem with my multimix 8. Anything I played through the mixer on phones sounded clean. It only happened with the audio output for the computer. I tried the aiso for all drivers with no luck. I just wrote off the mixer as a piece of shit and gave up. :(
Reaper rules. I don't know why they chose the honor system business model but it has earned them tons of enthusiastic supporters. It doesn't just do the job it kicks the job's ass. The built in plugins are pretty nice I use them pretty much exclusively now.
One option is electronic drums through a PA or amp. Then you could set the volume to be whatever you like. Maybe put mesh heads and triggers on the smaller kit?
Or earplugs. I wear earplugs at practice all the time.
Both my bro and the guitar player had theirs set up professionally. They tune to D sometimes, they rarely use standard tuning. They sacrifice a little playability in other tunings in order to have optimal performance in their preferred tuning.
I'm not sure I play synth and backing vox.:D
They have their guitars set up for drop C like Drew said action isn't too high at all. I'm personally not a fan though. The strings are just too loose. When I'm playing my bro's bass tuned to C I'll often push the low string right off the fretboard...
For me it's usually the bass. I only really record myself and the band so that's what seems to work for us. We play metal, the guitars and bass are tuned to drop C and the genera calls for more of a clicky kick so the bass gets the majority of the low end.
We usually do scratch tracks first. We try to get em right though. That way if they are good enough we can still use em. If they aren't good enough we can figure out why before we lay down the final tracks.
That looks like a UX2. That's a nice interface with decent pres, you can do a lot with that thing. I think you're set there for now.
Upgrade the monitors and treat the room next before messing with any more gear. You need to be able to hear what's going on before you can tell where your gear...
I made some portable traps by taking the seats off of some old rolling office chairs and bolting frames on them.
I also remember someone here posting pictures of a bass trap that they mounted in a corner with a door that would swing out of the way when you opened the door.
I don't know much theory other than note names and a few scales. Just enough so I can jam with people and communicate to some extent. I'd actually like to know a little more but to be honest it kinda bores me.
I'd like to be a little better about determining what key something is in. That would...