New chainset question

ContrelaMontre Posts: 3,027
edited July 2018 in Workshop
Hi, I want to convert my current Shimano sora triple chainset to a double setup on my Specialized Tricross CX bike.

I've been gifted an ultegra left crank stages powermeter. Am I ok to pair this with a Shimano FC-RS500 double chainset rather than an Ultegra one to keep costs down?

Do I need to get a new bottom bracket for this setup?

I already have some old levers and a double front derailleur to replace the triple.

Is there anything else I need to consider?

Rule No.10 // It never gets easier, you just go faster