I got the AMD 5200 dual and I couldn't be happier.  So far I have yet to really bog down in poser - I have the settings pretty high and haven't gone over about a 10 min render time.  Texture filtering hurt a bit but I think that was due to a bad chip of ram I had installed.

I cant stress enough though that I seriously seriously recommend skipping that whole box hp for 899.00 thing you mentioned - and just putting your own together.  Its really much easier in the long run when you personally know what is going on inside your machine.  And ALOT cheaper.

I am:  aka Velocity3d