5000

Finally, I'm able to render a 5000 spp image in a reasonable amount of time.  Here's my class test scene at 5000 spp, rendered in ~8 minutes.

For reference, smallpt (http://www.kevinbeason.com/smallpt/), which is similar to my tracer in that it only uses brute-force path tracing, renders the Cornell Box scene at 5000 spp in 124 minutes on the CPU.  Note that the resolution is ~2.5x my resolution, so taking that into account, I'm still about 6x faster, but my scene is obviously way more complex.  I mean, that's not really a fair comparison by any stretch of the imagination, but at least it proves that I'm not totally crazy to pursue path tracing on the GPU.