Hi Filip, yes I agree light intensity is more important, but 6500k gives balance between white, red and blue, so I'd disagree that it has little consequence. Some people prefer bluer light at around 10000k, and still manage success in planted tanks, others prefer 4000k. Surely if plants are looking more natural, it's because they're getting a more natural source of day light at 6500k? My advice was intended to simplified and PAR, PUR and lumens do tend to complicate things. 6500k is a very good starting point, and as mentioned, the lumens are pre determined by the manufacturer based on how wide the tank is. If I've annoyed you in any way, my apologies, that wasn't the intention...
Branch, I just realised you've bought a co2 kit for $750? Honestly, this isn't needed for swords and anubius. Root tabs are key to swords, not co2. And the right light of course. Good luck, what ever you decide