I have a credit score of 830, have been a AMEX card holder since I have been 18 (now 35) and myself and my wife make a combined income of $90,000 per year. Amex will not for the life of them increase my surpass limit from the current $8k to $10k (first asked for $15k six months ago) that I have asked for as of two days ago. I pay every card I own whether business or personal on time every month.

So far on my Surpass card I have spent $28k and when I hit $40k in July I'd like to drop them like a bad client and look at the Citi Reserve card to keep my Diamond status.

If I drop the Surpass card negatively hurt my credit as the limit is only $8k?
Will applying for the Citi Reserve negatively affect my credit?

If I do end up dropping AMEX how much money is one client worth to them if they spend $40k to $50k per year?