Hi,
Yes I agree a Motif Rack ES is a good host. I have one with a PLG150-AN and PLG150-VL in. Whilst the AWM engine is simpler than the one in my (older) EX5, it is capable of making some very nice sounds.
PLG programming is a bit of a faff, mind. Tou have to set up board voices and native voices. Boards lose their contents when they power down, unless you set the host to save the board memory, which slows down the host startup time. And you cannot read from the board, you can only write to it, so the editor is essential.
Cheers
Derek