Rain : "But I could - in theory - stretch this equilateral triangle a bit, and I'm wondering if there are any advantages, considering the fact that the monitors would be closer to the walls as a result. "
Things don't quite add up (not being picky, just want to know what's available)
Up top you said you had 2.5' between monitors and they were about 3' from the side walls. That makes 8.5' but your room is 11' wide ?
11 is a lot better than 9... If you have sufficient absortion on the walls you can probably get away with them being fairly close.
Especially since they'll be turn in quite a bit.
Stands would be a good idea, especially if it means you can get your monitors away for the desk.
My speakers sound awful with a desk in front of them compared to on stands with some space around them.
Your desk being small is good. Try and get your monitors as far to the sides and above your desk as you can.