I have a commute/light touring bike, currently with a square-taper triple. I'm thinking about fitting a 48/34, 11-34 9 speed double. As far as I can tell, currently only SRAM sell a new 48-34 crankset (VIA, Apex, or S-100). These need a GXP bottom bracket. I also can't find any information on price - could anyone hazard a guess at how much all of this would cost? Also, will it fit in my existing bottom bracket?

My other option is to buy new chainrings, and source a crank. It seems that 104mm BCD 48t outer chainrings are more common, so I suppose I would have to find a MTB double crank. I currently have a square taper BB, but it would be nice to go to a hollowtech one.

I would appreciate any comments on the above - am I missing anything? Should I stick with a triple?