> if the mat-04 could be used and just use half of the chip. It looks like they are basically 2 mat-02's in a single package
The specified noise of the -04 is significantly higher than the -02, for both low-Z and high-Z sources. The only place they are equal is in the few-K ohm area, and any transistor can do good there.
The specification may be fudged: the -04 may typically be better than it says. Or it may really be worse than the -02 because maybe they put the four devices on the same size die as the two devices in the -02. At these impedance levels, you want acres of silicon. (But you still want very-clean silicon, and you still want pretty-high Beta.)
If you trust the spec sheets, the only reason to use the -04 is when you need FOUR matched devices. It simplifies some analog computing work, and you might design a gain-cell around a quad. But for microphones, we want to of the very best, meaning the -02.
The -02 specifically says it can replace the LM395, "the other" low-noise dual. And the 395 isn't crap. So if you can't turn up a -02 for a price you can pay, shop for a 395. Check the pin-outs before you literally drop one into a board designed for another. EDIT: I mean 394 !!!
National has never given me a hassle for using their Samples program. If you are building a couple preamps, take the freebees.