I would consider a pair of used AT3031 cards. They are pretty good SDC's which go for a bargain-basement price of around $100 on eBay. They are made in Japan, and were replaced by the nearly identical AT4021, which sell for about $350 each. They are clean and detailed, have reasonable self-noise, and are very well made. Lots of times, I listen to past recordings I did with them and can't tell/remember (without looking it up) if I used them or if I used other SDC's that cost several times as much.
I haven't used the CM3, but keep in mind that it is wide card (somewhere between being cardioid and omni), and may not "focus" as clearly on one part of your ensemble as a true card would.
In any case, if the hall is not great, ORTF or NOS positioning make sense. You will have to play with how far out and how high to place your array in order to capture a balanced orchestra sound that is reasonably distinct from the choir (which you will be capturing separately with other mics, hopefully to other tracks for later mixdown). You might try your stand a little lower than normal if the choir is behind the orchestra and on risers, and maybe a little closer to the podium. That will give you plenty of string sound, fairly distinct from the choir (though your woodwinds might get a little lost - but, hey - it's a compromise however you do it with only a few mics). Strings are the "meat and potatoes" of the orchestra (unless you're a vegetarian, then they're the "tofu and veggie burgers" of the orchestra).
Make sure that you have clean, fast, quiet preamps with a reasonable amount of clean gain for the mics. Preamp noise comes into play with more distant mic'ing , quieter dynamics, bigger ensembles, and larger venues, so a stock audio interface's pre's might not cut it. If you need to pick up pre's as well, cheap options include the M-Audio DMP3, Symetrix SX202 or 302, or a pair of StudioProjects VTB1 pre's (if you go with these, keep the "tube blend" at solid state). I wouldn't overlook the pre's; I made plenty of noisy, smeared recordings with excellent mics before I was finally smart enough and financially able to buy good preamps.
Today, it's great that there are decent cheaper options.
Good luck with it,