You have to be on the Endgame Chapter to reach them. Arguably they're harder than the end game boss, but yeah. oo;
My first Fire Emblem was Sacred Stones. :3 Although, I solely relied on Seth at the time (because he was OP as all hell), and neglected to level up my other units, outside of strong ones like Myrrth and General Dussel. Lesson learned. x___x But, Sacred Stones is amazing as well. :3 Probably not my most favourite storyline, but, I loved Lyon. @___@
Owain and Inigo is hilarious; I agree with you there. :3 "DOWN O' MIGHTY SWORD HAND!!" Owain would say, and, you can imagine my reaction. XD
And Inigo, oh, that flirt. :3 The children are really, really strong though! I use Owain as a Swordsmaster and he married Cynthia (because they both pretend that they're heroes), and Severa is a Hero who married Inigo, another Hero. <3
Lucina's and the female Avatar's support is.. interesting. XD