"Yes, but only if you want a 40"+ monitor"
My currrent monitor wall is larger than that (4 x 17" 1280*1024 displays)
Replacing that with something that has slightly fewer pixels overall is justifiable simply on the grounds of not having to mess around with Xinerama and it'll have twice the height. Yes, it'd need a pricier video card to drive at more than 30Hz but it's still a viable option overall and I can retire the 4-headed quattro that Nvidia's given up supporting.
As for desk space: just mount it on a pole or something. I do that already - there are a few cheap-o monitor-arm suppliers kicking around so this isn't a £300 cost - more like £50