It really depends on the room you are putting it into. If you have a good plasma, then you may have certain expectations for black level performance, motion handling, image processing, etc.
The Epson will deliver better black levels and should have better color and image processing compared to the 131x, but the Optoma will do a bit better with motion because it is DLP.
But, the black levels won't match the Epson.
On the other hand, if your room is white, you have white ceilings, beige carpet, and your typical living room furniture and a couple of floor lamps, then you may want to go to your local movie theater and ask why it is they don't do that same setup...
Really, if you are doing a front projector, and you want top shelf results, then yes, the Epson is worth it, but only if the room is worth it, and if the room is worth it, then spend $500 more and get the JVC RS46 which will blow away the Epson and obliterate the Optoma. It actually IS worth the money spend. The Epson is nice because it does a solid job and has great zoom range and does a fair job with 3D, but the JVC simply rules with 2D performance and satisfactory 3D (despite what others may say).
If this is just your 'family room', then I'm not sure the Epson is worth it. You will get some benefit from the added black levels, but the light bounce if the room isn't properly treated, will bring contrast down a fair bit. You certainly will notice the improved black levels, but the room wouldn't warrant the extra cost IMO.