hi,
to my knowledge, the video card doesnt really affect render time that much, thats more of the processor u have, the video card is more for the onscreen display while working on a model. (pls correct me if im wrong guys!)
with your out of memory problem, well 256meg of ram will help, but try changing your virtual memory space in your operating system to a higher value. this space is set aside by the operating system just for calcuating large data processes. if u r using win2k or nt, it can be found by rite clicking the "my computer" icon. im currently running about 1.5gig of virtual memory, which u will find necessary for very complex renders.
also a defrag of ya harddrives every day is very useful, u'll be surprised on how badly windows handles memory and writes all over a disk. this will minimise the severe caching noise u hear, as the disk head can read a file in sequence, rather than hopping around the disk looking for space and parts of data
to finish off, im using a 32meg 3dlabs vx1 video card. i have had no problems with it. Very good value for money does the job of most high end grfx cards and the drivers come with preset settings for all of the 3d and some 2d applications. if u have the money, i suggest u go to the next model up in the series, but expect to pay about 3-4 times the price
good luck
ricardo