If there is a good savings on the 550-650W units, I agree you won't need more than that.
Seasonic has no good quality offerings in the midrange gold plus sector, since the Focus series has had its share of issues. A TXm is a solid choice. RMX would be even better.
If a Bitfenix Gold series could be had at a savings, grab that. Very good units and usually fairly inexpensive. (They are non-modular though!)
The 5700XT currently ONLY comes in blower models...
I love the look of the 200s on the CM H500. An MB520 is a solid option if it's a savings, though I think the Meshify C is comparable in price these days.