Overkill from my Structural Engineer, can you check his drawings?
The structural engineer sized that as a W6x25 steel beam because he wanted it flush in the 2x8 floor system as it is only 6.38" deep. If you changed it to a LVL, you would need a 3 ply 11-7/8" LVL, which would stick 4-5/8" below the floor system and you would have to build a soffit there.

The steel posts are there on either end because of large end reactions from these stacked beams. Your ridge beam in the roof stacks with your 2nd floor beam which stacks with your 1st floor existing beam/girder or whatever that is. If you really don't want to use steel posts, then you could ask him to size PSL or glulam columns as they might be an option too. If you're limited to 2x4 interior/exterios walls, then steel posts are sometimes your only option. 

If you add additional interior bearing and decrease some of the beam spans, you can reduce the size of the beams. Wide open floor plans, the lack of interior bearing, and the homeowner not wanting soffits, are all things that the structural engineer is thinking about while sizing/designing these beams.