Decently priced 300 blk upper?

My cousin is talking about getting is first AR and knowing that he isn't going to go shoot this thing every weekend or things like that but does appreciate things of decent quality and not just the most absolute dirt cheap solution. I directed him towards something like the M&P 15 in 556 but he would be interested in maybe having 300 blk as well. I told him his cheapest solution for a good setup would be to buy the M&P put an SSA-E in and then get an upper to put on it. Who would be a decent upper to buy that would about match the quality of the M&P 15.