i think maya or 3d max are what your are looking for as an external animation software, either of the two are very good though some folks do use it for technical vizualization its mostly used for movie special effects
however the learning curve is very steep a lot more than animator or photoworks plus to start with you will have to learn how to repurpose cad data to a format either programwill work with more easily ,normally polygons
you can import dxf into max or iges into maya but you need a big processor to cope with the cad heavy data you are bringing in
okino polytrans as mentioned above is what we use to get sw files into maya it keeps model trees intact as in the case of assemblies but also strips out unused entities and converts to polys and so aids significantly in the ipmort of large models
however you get dumb data in with no constraints, mates
or materials so then you have to rebuild a lot of assembly constraints and really work on materials and textures
however this is where the strength of the external animation software shines the results of using animator cant really compete with what you can achieve in something like maya or max also rendering is head and shoulders above what you can produce in photoworks
where it falls over is that if you make a design change to the model you have to go through the entire process again importing assembling reanimating re texturing it is as i said before dumb data and this isnt the case with animator or photoworks inside solidworks
you will see this adds considerable time to the project
mental ray is high end renderer as is renderman
both maya and max have mental ray 3.1 built in as a renderer, photoworks 2 is a very limited cut down version of mental ray from the parent company mental images
it is adequate for engineers wanting to produce nice images with fake global illumination(the bit that make your images look that bit more realistic)
renderman is the daddy think shrek and toy story and thats what renderman is for ,it supports a high end shading language and thats all it does render, to be able to get a good result is quite intense when you compare it to something which is simple like photoworks also its around 15,000 us dollars
I would examine what you want to achieve there is nothing simpler than photoworks and animator for producing animations with a polish on them
some companies need near broadcast quality for corporate presentation or super realistic images that look real ie not computer generated for product launches
If you arent into that then whilst maya and maxarent that much more expensive than buying the photoworks and animator add ins i would say its not worth the effort
and would learn the animator product and photoworks quite good results can be achieved with it