So I'm moving to Seattle in a few weeks, and figured I'd rack up enough organic spend to hit a credit card spend requirement, and I'm a little stumped on what to acquire. I currently hold a CSR and a Citi Prestige. I'm at 2/24 and 0/90 for Chase and Amex respectively, I will mainly fly AS/UA going forward (SEA-IAD/SEA-SFO-TPAC) and my preferred hotel chain is SPG/Marriott.

• United Explorer -- will eventually need this anyway in 2019 for the PQD waiver, assuming I can pay my rent on the card.
• Ink Business Preferred -- 80k points sounds great, but I'm nervous about the validity of the whole "sole proprietor" thing.
• Marriott Rewards -- mainly only useful for the 15 night elite credit toward lifetime status, again, UA Gold matches to Marriott Gold.
• Amex SPG Luxury -- confers Gold Status, but not available until end of August, and not sure if the credit can be used for bookings.
• Amex Platinum -- mainly for Centurion Lounge access (esp. SFO/HKG) as UA Gold matches to Marriott Gold (for now, anyway).

It seems like the logical choice is the UA or Ink card, thought I'd appreciate any advice anyone might have on the matter. I've been fishing for the 100k Amex Plat offer for a while now, but no luck, though I haven't tried with the new address yet.

Not sure if advice threads are permitted here -- if not, mods please lock/delete/move/whatever.