Not a problem at all — always nice to see another home network admin who is not willing to settle for flaky wifi!
So that's actually a really good question. Here's my take on it. Historically, channels 36-48 (at least in the USA) are lower transmit power than the rest of the 5GHz channels. As a result, they're the least appropriate for penetrating walls, but on the bright side, it's really really unlikely that your neighbors' networks would interfere with you on these channels. However, recently (like almost a year ago) the FCC has made a recommendation that you can actually transmit higher power on channels 36-48. However, I've yet to see any AP's actually take advantage of this — in the syslog when a Ruckus AP boots, it prints out a channel list and the transmit power per channel, and it still shows 36-48 as the lowest transmit power 5GHZ channels. Note that, not surprisingly, some consumer AP's and custom firmware have no regard for FCC transmit power limits, but that's another can of worms.
On the other end of the spectrum, channels 149 to 161 have come into great popularity because the FCC lets you transmit at a pretty high power (the highest power of any of the 5GHz channels). You can get *almost* 2.4GHZ-like coverage on these channels. On the flipside, I've found there's a lot more non-802.11 5GHz interference up at these channels. I believe the first generation of DECT cordless phones (the ones that called themselves 5GHz or 6GHz) transmitted around this range. Note that newer DECT "5.0" cordless phones transmit at 1.9GHz and don't interfere with wifi at all. But of course, you can't exactly knock on your neighbor's door and ask them to upgrade their cordless phones!
The DFS channels are in between this range, and the regulatory power is also in between, making them excellent channels to use. What makes them even better is that DFS channels require AP's to detect military radar usage that is on this band (and switch to another channel if interference is detected). In practice, this is complicated and you have to pay more to be FCC certified to operate on DFS, so most consumer AP's don't bother. This is a blessing if you live in a crowded apartment complex like me, where all the other 5GHz channels are flooded with my neighbors' AP's but the DFS channels are nearly empty. It's also nice because 802.11ac lets you run super wide 80MHz channels, and there's only a few of those if you don't use DFS. Even if you don't have neighbors, if you plan on expanding past 2 or 3 access points, you might find yourself with co-channel interference if you can't use DFS channels.
In your network with 2 R500's, all of these channels should work fine for you. If you only had 1 AP, I would suggest using one of the channels 52 or higher, especially the 149-161 channels if they are clean in your area.
Hope this info helps!