I think I know what you're looking for, something minimalistic but with a bit more flare than the Define XL right?
800d and switch 810 (special edition matte black/gunmetal finish) fits all those points you're looking for, but there are a lot of advantages and disadvantages between the two cases.
1.) The build quality of switch 810 is fine but the 800D is decidedly better.
2.) If you're planning to liquid cool then you don't have to worry too much about noise regardless, but the 800D is a pretty closed case and you can open/close the top cover on the switch 810 to either shave off some ambient noise or increase cooling performance.
3.) The 800D is a great closed loop chassis but the switch 810 has a lot more support for liquid cooling (you can add a triple rad on the top, single rad on the back, dual rad on the bottom) you would need to research the rad thickness permitted in the case I forget how much it was.
NZXT Switch 810 Review & Watercooling Guide - YouTube
4.) The 800D is about 2 inches bigger in height and length than the Define XL and the Switch 810 is about 1 inch bigger in height and length. So not that much bigger than the XL, still a good size without being an eye sore. Aesthetically, I think the 800D looks better but if you get the Switch 810 in the special edition matte/gunmetal finish they're both comparably professional and minimalistic looking.
5.) As for features, both have support for USB 3.0 but you'd need to buy an upgrade for the 800D IIRC, the switch 810 has easy to access/clean filters, both have hot swappable drive bays, and both have large grommets and good space for cable management however, the switch 810 has superior support for air cooling. The switch 810 comes in about 180$ (if you're lucky you can get one on sale for 169.99 or 129.99) and the 800D around 270$.
Sources: I own the Switch 810, friend owned the 800D.
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