Vertex Omega is a nice unit. I would go for the Vertex Puratek RO/DI unit. It has everything included with the unit and an awesome 1:1 good water to waste water production. As for powerheads, I wouldn't go MP40's... Not in a 70G. That is WAY overkill and too much money IMO. I am a Tunze fan but even then, I think 2 - WP25's would be perfect. Just have them mounted off the back wall, in the corners, facing near the middle of the front glass. That will give you lots of nice flow.
As for a doser, I am thinking a Kaomer or spend the extra $100 and get a GHL Doser. They are well built units but hear good things about the Kaomer as well. In total, thats probbably $1200 plus tax or so... For the return pump, get the Water Blaster or a Waveline. Both run exceptionally quiet. Water Blaster comes with 3 yr warranty but Waveine is controllable.... Mind you, controllable for a Return pump is a little redundant IMO. You generally want it to run wide open 24/7. Get a return pump large enough to run your reactors as well. Saves space, prevents excess heat, less hydro and less maintenance.