i want to make some scenes where there are two characters in a dark room (a bar) and there are other characters lookin on. the lights would be primarily on the two characters.

is there a good way to do this. it seems like trying this would make poser 8 crash.

or am i overthinking this....

Don't believe you are overthinking this.  You will need to go low poly with the remainder of your populated scene, especially if they bear no relevence to the main characters.  The original Vicky and Michael might fill that need.  Also, textures should be low res to ease the render load.  If you think this might be too intensive, try render passes of back-, mid-, and foreground and combining the images in a 2d program.  Your workflow approach is just as important as your set, and you should explore other options if your original concept doesn't work out.

Whilst I must admit that I have never done a proper crowd scene, I think the answer is to use some kind of layering. Rendering 1,2,3, or more characters at a time, then using that render as a 2D element in the next render, to which two (for example) new characters are added. There are various ways to integrate the 2D images. Pasting them into square primitives  in the scene, or pasting them into the Poser background, or assembling them in a paint program as layers, or a combination of the above.

Which ever method is used, careful consideration needs to be given to what will be included in each layer, and what things in one layer will occlude elements in other layers. Shadows can be a problem in these methods.

I've been successful in rendering 8 full-poly characters in a doctor's waiting room, all of which was modeled. The PZ3 was about 550 Meg. But then I've got 8 Meg of memory and a 64 bit OS to use it.

Adding to ideas above, you might render the background and import that render as the background image for your final render. That might work if you don't want to composite it in a 2d app.

Lastly, Daz has some great low-poly characters... a low rez male and Loretta Lorez. I've used both as background characters and been quite happy with the results.

There are some vendors here who sell something like what lesbentley described. You might find them useful. Search under "Crowd" and you'll get some hits in the marketplace like this

http://market.renderosity.com/mod/bcs/index.php?ViewProduct=16623&keyword=crowd&list=keyword

http://market.renderosity.com/mod/bcs/index.php?ViewProduct=71815&keyword=crowd&list=keyword

Good luck

 The problem with the above two products is, you can't pose the characters. They are pre-rendered and wysiwyg.