Why do you think you need LP RAM? While it would probably help a bit in ease of building, possibly cable routing, and so on, I don't see tall RAM being an issue in a Cerberus with a U9s. The cooler is built for complete RAM compatibility, so there shouldn't be any interference there.
As you can see the front fan is entirely within the bounds of the mounting bracket (and thus the socket keep-out zone), and won't touch your RAM. The "rear" fan might possibly interfere with large VRM heatsinks/rear I/O covers on some motherboards, but that should be fixable by shifting the fan up a bit.
As for speed and latency, it's mostly a wash when they're that close. Back when AnandTech did their in-depth memory scaling reviews (
like this) they used a "Memory performance index" calculated by effective frequency / CL, which in testing was a pretty decent predictor of performance (outside of very low frequencies or very high latencies). The kits you mention are 3200/16 = 200 and 3000/15 = 200 - i.e. likely to perform identically. Often lower latency kits (like a 3200C14 vs. 3200 C16) have better DRAM chips, but when the numbers are this close there's no real way of telling. In all likelhood they'll perform exactly the same. How well they tune/overclock is of course impossible to predict.
Still, if you can use more than 32GB of RAM and have the money, you're getting more GB/$ with the 64GB kit.
- it shows you care more about performance than style.
smallformfactor.net
