Having used a lot of different mics, I can safely say that dynamic mics are generally not generating enough signal to mess up mic pre-amps. While there might be some variation in level (due to impedance difference for example or just a higher output capsule), with 20dB of headroom I don’t think you should normally run into any problems gaining the mic channel and with both channels having their own mic gain, using two different mics should also not be a problem.
I own both DDJ-SX and MCX8000 (guess which one I am phasing out? LOL) and I can safely say that the SX is giving me more mic headaches than the 8000.
As Gee stated, most all wireless mic receivers allow for a healthy dose of attenuation on the receiver, again making it relatively easy to match mic and mic pre-amp. Sometimes they will have a (extra) option on the back to set output signal level.
Finally you can use wired mics with condenser technology that have batteries to power them. These too should not output levels so high the pre-amp can’t handle them (built-in pads and other options).
Also I am assuming that the problem you mention is that of feedback. This is a problem that has very little to do with the output level of the microphone, but more with type of mic and sensitivity, as well as where you place yourself.
Without going into a full workshop on feedback (prevention), unless you need vocals to sing through a mic as a DJ (I would opt for a small PA mixer to add to your setup - more on this further on), these are the main guidelines when it comes to mics:
- Use cardioid or - even better - supercardioid mics (this is the direction in which the mic is most sensitive)
- Don’t cup your hand around the mic “rapper-style” as this will turn any mic into an omnidirectional one and really mess up your feedback issues
- You and others that use the mic should be instructed on use close-mic technique. This means holding the mic under your mouth, against your chin, angled up at about 45 degrees. So effectively so speak OVER the mic instead of directly into it.
- Use dynamic mics! While it’s nice to use higher capacity mics (like condensers) they are SO much more sensitive than dynamic mics, they should only be used by professionals in a professional environment (like stage or studio). I have dynamic mics I can use almost right in front of the speakers (always a bad idea, see point 5) and I have used condensers that would feedback from the back of the room.
- Do NOT stand in front of the speaker and preferably not with your back to a speaker. The supercardioid mics are most sensitive to sound coming directly from in front of the mic. If you are standing somewhere with your back to the speaker(s), that sound comes around you and mixes with your voice and then comes out the speakers reinforced and -presto!- feedback.
- Finally, but more to prevent “pop” sounds (p’s and b’s mainly) and for hygiene reasons, always use a pop filter/windshield
Well, quite a wall of text and I hope it helps you and/or others, so I’ll finish up now with my final advice.
Sometimes it is good to acknowledge that you need specific gear if you have specific needs, rather than expect that what gear you have will do the trick. I do believe (and know from experience) that the MCX8000 is pretty good at handling mics that are good for DJs. As soon as you need more functionality, it is worth adding a small PA mixer. My current favorite for two mic use is the Yamaha AG06. This will give you professional level mic control (including FX and EQ that you can set on your laptop once and then use with simple on/off button) with built-in pad, phantom power (if you insist on using condenser mics), both gain and level. Hook your mixer/controller output on the stereo (RCA) channel and the mics to the mic channel and you will have plenty of control over all your signal levels. It is also great to hook up iphone/ipad/ipad or something with a pre-recorded mix for backup purposes.
Oh, and at a price of about 125 euro they are very reasonably priced (did I mention you can connect through USB and use them as your desktop sound card and/or record the master out signal?). If you don’t want the bells and whistles and USB-sound card, the MG06 is a great alternative at around 80 euro.
Long read (if you made it to here), so I hope it was helpful in some way.
As always, just my two cents worth.