Poser6-SR1 is the first Poser 6 patch, it might be necessary if you've had any memory problems with poser, but I can't remember if there was anything else in it that made it necessary. P6CU1_M had some files that were accidentally left out of P6 when it was released. Depending on how recently you got P6 you may or may not need it.

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If you're joking that's just cruel, but if you're being sarcastic, that's even worse.