Aero Precision Lower and DPMS Upper? How do they match?

[TheGewehrGuy]

I am looking at buying an A2 configuration completed upper (minus bolt carrier and charging handle) off of gunbroker, then take apart my current AR upper, with the end result of selling my 5.56 barrel somewhere (Only 500 rounds through it), buying a 6.8 SPC barrel (maybe a 7.62x39, not sure), with the end result of a basically:

Military styled, A2 upper
6.8 spc (or 7.62x39) Tactical Styled upper

What do you guys think of that?

Also, the lower I have is an Aero Precision, and I am hoping that the shades of black and the tightness match up somewhat well. I know it doesn't really matter much, but I have seen some night and day, lower/upper combos.

Thanks