Ordering i beam for support?

Took out a fireplace in a two story home on the bottom floor that had a load bearing post on one corner consisting of two 2x4 in the center of a 20 ft span. This is the bottom story of a 2 story house in central texas so there is no snow load and was calculating off the standard live load and dead loads of 30/10 psf ??? Second story floor is on 16" centers and we have a clear span of 20 ft on the bottom floor with 8' ceilings so headroom is of the utmost importance. Planned on reinforcing under theouter wall on one side to carry the additional weight of the beam and installing a 4" post mounted to the floor on the other side to carry the weight of the beam as well, even though there is currently a wall with 10" of support currently there but composed of wood. Keep getting 8x48 beam but it just sounds like complete overkill seeing as how just two 2x4 are supporting the 2 2x10s running the span now ? Any ideas , completely understand that an engineer should look at it and have had two do so already via contractors whom seem to not be very interested so this has now become an in home project.