The best thing to do is to sign up for multiple credit cards for their sign up bonuses. That is going to get you the most value. I second what @becauseimnew said. The CSP is at an all time high and if you can refer to Player 2 that would get you a lot of UR Points with Chase, which are highly valuable. But there are rules to signing up for different cards so run everything through us here and we can help.
One question would be when do you plan on the $20,000 spend. Now or spread out over a year.... this will help in recommending cards also.
Definitely looking at CSP, I think I will start with that and see if Player 2 wants to join as well. Unfortunately I waited too long to truly start this process and now I have 60 days before I am getting married. Everything will be paid within 30-60 days so i'm on a bit of a time crunch.