It looks like I can get about 40 ksps, so it is far more than enough for my purposes.
The guy who wrote the code got about 62 ksps.
40 ksps * 2 bytes = 80 kilobytes/second = 640 kilobits/second
I assume I can fit this within the SD card throughput (altho this is way more than I need), but I'm not sure as I haven't been able to find any hard numbers. I've only seen someone mention they can get 150 Kbytes/second write speeds, again way more than enough.
Am I missing anything else? Will I be overtaxed trying to do input simultaneously with output?