So I just changed my resolution to 3200*1024 with the info presented here:
http://forums.spiralknights.com/en/node/179#comment-26172
It looks pretty cool and seems to work fine, so perhaps add a way to change that via the ingame menu!
(I remember my old nvidia card had issues with spanning game windows across several monitors though (even if it just peeked a bit over to a seperate monitor, but my current ati card does it fine this game)

have a screenshot:
http://imageshack.us/photo/my-images/8/widescreenf.jpg/