The Sonosax SX-M2/LS2 (aka Lemosax) option in the YS would work, too:
http://taperssection.com/index.php?topic=141111.0And there may even be an NBox option in the YS somewhere, but I haven't looked. Both the SX-M2/LS2 and NBox are preamps containing circuitry that replaces the mic body DSatz notes in his post. In both options, you need specialized cables to connect the MK4 caps to the preamps. I believe both YS listings include these cables.
One of the primary benefits of using the MK4 cap is that it's part of a modular system. So if you have MK4 + associated cables + Lemosax (or NBox or CMR), you could replace the MK4 with another set of caps, if you wish -- for example the more directional MK41 supercardioid. Typically, it's less expensive to replace the caps vs. an entire mic.
If you're happy with using strictly cardioids, you might also consider the CCM4, which is not modular like the MK4. It's a complete microphone, albeit still very small. It can be used with any preamp providing phantom power -- Sound Devices MP-2 or MixPre and Naiant LittleBox are two options that spring to mind. Fewer specialized components with this option, but you lose the modularity of the MK4 caps. In this option, if you wanted to switch to supercardioids, you'd buy the CCM41...but this is more expensive, since you're buying the entire microphone and not just the cap.
So, to sum up:
- MKx for modularity, but requires more specialized components, i.e. limited number of preamps and specialized cables.
- CCMx for a more standard option usable with any preamp providing phantom power, but at the expense of modularity.