Dude, if you're going after a Define XL, you can stuff a 480mm Rad into the top OR front of the thing.
Stick a 420mm in there with three nice Noctua 140mms and call it a done deal.
If that's not QUITE enough rad space for you, stick a 280 up front.
Sticking with 140mm-multiuple setups gives you maximum airflow and surface area, as well as lower overall noise and fewer fans.
Note: Common wisdom is 2x120mm per device being cooled on your loop.
For CPU + GPU, you're looking at 480mm. A 480mm rad works out to 57,600 square mm.
However, a 420mm rad works out to 58,800 square mm.
So it'll work roughly the same as a 480mm for your requirements.
Last year, I had a big chunk of my build budget slashed by some unexpected bills.
So I wound up going with a 420mm Alphacool AIO setup instead.
Not as spiffy as the hard tube setup I was planning. But was a fraction of the price.
And as I mentioned, whatever you wind up doing, dump default fans in the system for Noctuas.
If you hate the doo doo brown, go with the Reduxes.
TotallyWorthIt