Really no point to buying a 2600X if you're going to totally handicap it with single channel 2400 MHZ RAM.
My point is that "generally" people who have high spec PCs, are the people who like to stand tall. They treat their specifications like a competition in itself. The numbers don't lie, that is true. However you are simply gaining a few more FPS in reality, for high or low spec PCs it is almost impossible to see the difference by the naked eye. Yes you will get a higher benchmark score on Unigine Heaven, if that means the world to you then money is irrelevant anyway. So if you can save enough money by buying the lower frequency RAM, save the money. If you want to compare how great your benchmark scores are, then go for the faster RAM. Your experience however will be exactly the same.
The Consumer Rights Act 2015 gives you protection against these sort of fees. It clearly states you have 30 days to return an item that is not compatible. i.e Fit for purpose. CCL should of offered to help you resolve any compatibility issues. If not you can demand a full refund. I understand your thinking. You are guarding against spending £5 here, £10 there, £20 here and suddenly you have put up the price by a few hundred pounds for 2% extra performane. I get that. However Ryzen scales so positively up to a point using faster memory with higher speeds and better memory timings. It is the opinion of many reviewers - worth the extra spend. Yes in some situations neither higher memory speed or better memory timings are going to help. Sometimes one or the other will help and in certain situations both. You can be looking at 20%+ performance in those situations (benchmarks, certain games and things like zipping/compressing files). If we exclude those outliers and say you get a typical 5% boost between 2133MHz and 3200MHz with better timings. You should of course choose the faster memory kit. Think of it this way. If you are spending £1000 on a new system with 2133Mhz memory. It would cost just £35, or 3.5% extra for 5%+ performance boost. There are few other ways (after market CPU cooler with a small overclock maybe?) you can spend £35 extra on a £1000 Ryzen build and get such a large performance boost.
As another Ryzen user with "direct experience" in mutliple RAM speeds (Hynix and Bdie kits at 2133, 2400, 2666, 2933, 3200, 3333 and 3466 just on my setups, though 3466 wasn't stable enough to use daily) and combinations across multiple setups (R5 1600 and R7 2700x, with GTX970 and 1070ti, at various resolutions from 1080p to 4k) ... I can tell you WITH ABSOLUTE CERTAINTY that you can see the difference in performance with higher RAM frequency and tuning. Correctly setting high frequency RAM with custom primary and secondary timings made a larger performance difference than any overclocking of the CPU period. Don't listen to anyone who tells you to use slow RAM on Ryzen. They unequivocally don't know what they're talking about. The 20game average from 2133mhz XMP RAM to 3333mhz tuned RAM is approximately 30% increase: 2133 XMP - 0.1% = 55.2fps, 1% = 77.3fps, Avg = 123.65fps 3333 Tuned - 0.1% = 82fps, 1% = 105.5fps, Avg = 163.5fps 0.1% lows gained 39%. 1% lows gained 30%, Averages gained 28% So even if you're trying to play games at 60fps locked with Vsync on, you will need to jump up to 2666mhz with tuned RAM minimum. For those of use with higher resolution setups, especially those which come with higher resolution textures and assets streaming in more frequently, the faster the better. If you're striving for 100hz or above, there's no discussion at all anymore: fast RAM is now essential. Ryzen's architectural bottleneck is the Infinity Fabric which is tied to the RAM frequency. Faster RAM allows faster communication between the cores, and lower latency RAM decreases the wait time between specific calculations (very rough description). IF whatever you're doing isn't stressing the CPU but rather the GPU, you won't notice, but as soon as the CPU becomes the bottleneck, your RAM speed with impact how that bottleneck affects performance (ie: faster RAM minimises the length and depth of that bottleneck). Personally, I went with 3200 CL14 Samsung Bdie that I custom tuned, because that's where the best performance comes in (afterwhich the diminishing returns kick in greatly). For most users, getting 3000mhz CL16 RAM and using custom tuned timings will provide the bulk of your needs, and for a minimum or fractional increase in price compared with the slowest RAM; (excluding unusual outliers) the cheapest 16gb 3000mhz RAM kit is £126 while the 2400mhz kits are around £5-10 less. It's a no brainer.
Fair enough if it's working for you. But I got mine and it died after about 2 weeks, which I attribute to it not being able to take the XMP for my RAM. The VRMs are supposed to be terrible. Not to mention the BIOS interface is so dated. But I got it RMAd and sold it to buy a B450.