I bought a Strix X299-XE about a year ago, and at the time dropped in a single 64GB 4x16GB kit from the QVL, as I didn't have a spare $900 to throw at another 64GB & hoped that memory prices would eventually come back down to earth.

That kit is a Corsair DDR4 3466 CMK64GX4M4B3466C16, with 16-18-18-36 timings (https://www.newegg.com/Product/Product.aspx?Item=N82E16820236051), and seems to be working well enough, running quad channel at 3200, according to CPU-Z. Unfortunately, it's no longer being sold by NewEgg, and is in fact *more* expensive at Amazon now. So I may eventually be stuck buying a mismatched kit when going up to 128GB. I know this isn't ideal - but neither is not being a millionaire.

Questions - the context for which is: I'm not looking to overclock anything. I'm glad that my current kit is running quad channel at something close to its rated freq, but I realize that such differences are incremental. If there's a goal, it's to run fast enough that I don't feel like I threw a bunch of money away.

1) What are the most important specs to match? For instance, I'm noticing that the 3333/3466 G.Skill kits from the QVL are 16-18-18-38. (So, same as what I have, except the 36/38.) Assuming the CAS & voltage are the same, are the max freq & other numbers critical, given my goal above?

2) How much weight should I give the QVL anyway? For instance: although G.Skill makes 3200 CAS 16 64GB kits, only their CAS 14 & 15 are on the QVL. I'm also spotting that there will be a number of similar-looking kits from the same manufacturer, and the ones with the lights & bling generally don't make the QVL (and are often cheaper). It seems like there's probably a lot of "this is what we got around to testing". (Would be nice if they had an "anit-QVL" for failed tests, too.)

3) How does this all dovetail with the quad-channel capabilities of the board? I've got my current kit every-other-slot & running quad. Is the other set of slots semi-independent in any way, or if I pick wrong and can only get dual-channel with the new kits, does that hamstring the whole system?

I'd consider buying a new 8-stick 128GB kit, and trying to sell my current one on eBay, but the choices for 8-stick kits are even slimmer, and in some cases don't seem to be a performance guarantee anyway... For instance, here's an 8-stick kit from the QVL, but it only claims to be dual channel: https://www.newegg.com/Product/Product.aspx?Item=N82E16820236159