Since this buy is about to close, I am going to make a last minute desperation pitch for the acidulated malt. It's my go-to option for controlling mash pH for almost all my brews since I don't brew a lot of beers darker than SRM 6 or 7 besides the occasional Scharzbier or Doppelbock. It's super simple to use, I typically just use between 3 and 6 ounces per mash (5.5 gallon batch) and for me, it beats measuring out lactic acid (which is blasphemy anyways since it breaks the rules of the Reinheitsgebot). If you need more convincing to get in on the acidulated malt split, I don't know about your LHBS but at mine it is the most expensive malt, so 5lbs from the group buy split is a steal!
Also, if you want to make an awesome Koelsch, grab some of the Koelsch malt split!
Cheers!