if you plan on doing both, i say stroker first then BB. especially if you get a port job. because if you run a ported BB and add a stroker crank later...your portjob is now f-ed. it throws it all off.......plus if you do a stock cylinder, ported, and a stroker crank, you can make 30+hp with the right setup. and you can have teh stock cylinder resleeved for a BB sleeve and end up with a ported BB stroker. you may however have to have the portjob adjusted, may not...depends on what you're looking to do.
btw. 30 hp is right around double what it is stock...if i remember correctly....
i have seen BB strokers make 50+ hp......