Here are some tips I came across while going down this path and some comparisons of the different driver combinations I tried. I’m going to limit the comparisons to the 1964 Ears drivers for simplicity, but I noticed the same nuances between driver offerings from each of the companies I tried.
Tips:
1. Clean your ears. I know it sounds dumb, but hear me out. I had a friend who is a registered nurse look at my ears before I went to have the molds done and I had a full obstruction blocking my ear drum in each ear. I was recommended DeBrox, which is just a solution you put in your ears to loosen up hardened wax. PARENTAL WARNING: This isn’t pretty. What came out of my ears was a large, dark block of wax about the size of my pinky fingernail. I got one from each ear. The DeBrox came with a special syringe that you can use to flush water through your ear on a regular basis to help keep them clean. I’ll never let a build up like those happen again!
2. Know how much you can spend and save up BEFORE hand. The worst thing that may happen is you save up for 6-drivers, and then decide on only getting the quads. That’s what I did, and my wife enjoyed the nice dinner we went to with the excess.
3. If you have the chance to visit and audio festival or convention where the companies are, DO IT! It was unbelievably helpful to sit down and listen to how 6-drivers sounds compared to 4, or 3, or 2 drivers.
4. If using the mini-mixer (or wireless for that matter) it may not be a bad idea to put a limiter in the mix feed somewhere (I've never done this, so I don't know where it would go) as one poster mentioned below, one wrong twist of a knob could destroy your hearing, a limiter could prevent this.
Comparisons (1964 Ears products):
At the show I tried the triple, quad, and six driver options (not the duals though). Here’s my comparison between them.
6’s: 2 Low, 2 Mid, and 2 High Drivers per ear. These offered amazing clarity and near perfect balance. They were like sitting in front of a pair of really nice studio reference monitors. Everything was there, crisp highs with an airy quality, defined mids that tied everything together, and defined lows. The lows weren’t what I’d call “thundering” but were impossible to miss. Plenty of tightness and definition down low. If I sang, or maybe played keys, the 6’s would’ve been the ultimate choice for me.
Quads: 2 Low, 1 Mid, 1 High driver per ear. These absolutely were what I’d call “thundering.” They had a little less air in the top, but the real difference between these and the 6’s was the amount of bass. These do not sound like your missing a high and a mid driver, but rather sound like you’ve added a low driver for bass. The clarity is still amazing, and the bass is still focused, but these felt MUCH closer to the feeling of standing in front of an amp rather than studio monitors.
Triples: 1 Low, 1 Mid, 1 High driver per ear. The triples had the balance of the 6’s but with less openness to the sound. These sounded like what you’d expect really nice headphones to sound like. They lacked the thunder of the quads, but certainly would suffice as an IEM choice if your budget was tight. These really seemed perfect for singers IMO.
Here's a scan of there current product guide that I picked up at the show.