Well I'm supposed to be studying, and for doing so I decided to give myself a reward by playing Fire Emblem for a while yesterday.
I bought the limit breaker DLC and my, it was a very good training map for my Avatar and this one other sorceror with Nosferatu. Saves me a lot of time grinding otherwise. No regrets with this purchase!
My favorites are LB3, SB3, and RR3. LB3 is pretty standard. SB3 is great for grinding non-Chrom supports while you grind level-ups since you can place Chrom away from the action inside one of the cubicles. RR3 is pretty hard for most units though. I usually only use it to grind if I need more LB books.
I wish there was a way to turn off those stupid quotes from SpotPass characters though.
What the others have said is true. However, if you mean their quotes when they die as Allied units, you can't turn those off, to the best of my knowledge. The best way to avoid them is to avoid grinding on maps with Allied units.