I know that the RCA DTC-100 works fine with the Infocus LP340.
I believe that all other STB's will work with it as well but only have personal experience with the RCA.
At this time, I cannot see many benefits to other STB's, beyond the fact that the DTC-100 does not have component output. But you don't need component output for the LP340 since it does not have component inputs!
The latest edition of the Perfect Vision has a shootout between 4 new STB's. I suggest taking a look at it.