Centurion concierge for free = amazing value

Admiral's Club would also work well for me. between it and Plat, you could fly anything but UA/US (or LCC) and have lounge access.

IMO Merrill has 2 GREAT awards
-RC stays (much lower redemption rate than AMEX)
-MarquisJet (cheaper charters than Bombardier (AMEX's partner), and Merrill also has occasional promos, where redemption rates drop)

so for me, Merrill is the best backup card to AMEX (SPG and Plat)

i like the benefits of Saks WEMC and Lexus VI Sig, but they dont have good awards. (ill probably get them, but not carry them)