If AGR status is not important then probably a card like the Sapphire Reserve is better than the AGR card even for Amtrak travel and definitely for travel spanning multiple services from multiple companies in any cases.
Honestly, after comparing at least the CSP vs. the AGR paid card, I came to the conclusion that the AGR card had more worthwhile benefits for me, and Amtrak is by no means a primary mode of intercity travel for me. It basically came down to the fact that every dollar earns one AGR point, which I can reliably convert to 2.5 cents of value. (If I remember right, an AGR point usually comes in at around 2.9 cents per point when compared to the Value fare, but I always take a little bit off because of potential Saver fares, loss of the NARP discount, etc.) Even with the CSP transfer partners, anything above 1.25 to 1.5 cents/point required finding sweet spots in programs that weren't terribly applicable to me. The CSR does come with a bit more offerings, but the annual fee is higher ($150 after deducting the $300 credit for travel expenses) and most of the other benefits aren't selling points to me (I only fly a few times a year, so lounge access isn't crucial, and the Pre/GE reimbursement doesn't apply to me as I have NEXUS.)
That said, I rarely travel internationally, so the international redemption options don't appeal to me, and most of my domestic routes have ULCC competition that drives down the price such that redeeming points doesn't result in a good value. I'm also usually fine with cheap hotels, so it's tough to get true value out of hotel redemptions. The AGR card works because I want to take Amtrak specifically at least a time or two a year, and the Amtrak card does give a good daily spend value for AGR points/redemptions.
