If you matched speed/size you could get away using a different brand memory dimm but it's not advised like you said. If you really want to up it to 32GB, then go for it. I'm guessing your question is more along the lines of if 200MHz is worth the extra ~30 bucks. For one, I haven't shopped memory in a year, but it seems prices have gone down as I think I paid around $120 for 2x 8 GB. I don't remember the speed off my head but I did get LED dimms though, maybe that added to the price but if I recall that price was pretty average at the time. I would say, if 30 bucks isn't going to break your bank, get the faster memory, but if this upgrade is under a tight budget, you aren't going to lose any sleep going with the slower memory. You're still getting a good upgrade.
As for the price rise, could be cost of parts have gone up. Or could just be low stock so they upped the price, that link says only 1 left. Could be other things too, who knows.