First Gravel Race Bike

I have been a bike courier for about 15 years and I want to start racing gravel. My budget is around $4k. I am 6' 4.5" tall, 255lb, 38 years old. I have test rode a 64cm Surly Midnight Special, a Salsa Cutthroat and an All City something or other, can't recall the name right now. All of these seemed pretty nice but I don't know what I don't know so throw some recommendations at me, please & thanks!