I'd get the Dell 30" 3007.
Dell 30": 4,200,000 Pixels (2500x1680) in a 30" space = ~140,000
Westy 37": 2,052,000 Pixels (1900x1080) in a 37" space = ~55,500
The Dell has 2.5 times more pixels considering the space of the display. Plus, I think, that the extra 7" will be wasted anyway and if you plan on going with SLi'd 8800GTX's or CrossFire'd R600's down the road you'd better get the higher resolution display to really show off there power and the extreme high definition will look amazing if you hook up a PlayStation 3, Nintendo Wii, or Xbox 360.
image how big a upgrade itll be upgrading to the 24' Dell for me =)
Only way id be able to get the 30' Dell is if i could use it for a pc monitor / tv.