Says the poor man.

j/k. But seriously, the gunnar is $750 for just the frame.
Riv's Sam Hillborne is $1250 for the frame AND fork and headset. And you get the pretty lugs and paint job and Riv's geometry if that's what you like.
So the gunnar is a great bike, but if what you really want is a Riv, you don't need to spend much more at all to get it. If it was me, I'd spend a little more on the frame now, and upgrade components later if you need to save some cash somewhere.