The 2150 is Epson's entry level Home theater class projector the 3000 series is the next level up not a signifent improvement but much more refined. The 3100 has no fixed off set so with out using the lens shift it needs to be exactly in the center of the screen both horizontally and vertically. But it has a +/- 60% vertical lens shift so it can be placed anywhere from 10% of screen height above or below the screen or anywhere in between upside down or right side up. The 2150 has a fixed off set so it must be inverted if near the top of the screen or right side up close to the bottom of the screen and can't be anywhere in between without using the image robing digital keystone by tilting the projector from level.
"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS