Problem with thes filters (and other third party AE plug ins) is that they don't take any advantage of the video card.
Matrox RT2 WILL NOT make your render faster. It works only for its own filters (and will demand a good video card anyway) and allows to play lossless sd files and hdv files in real time when adding some filters and/or several tracks.
AE 7 has a better render engine, and AE CS3 allows u to take advantage of multicore/multipocessor, u could try to get a tryout version and find out how it works on your pc.
Finally your system looks OK (IMO), i'm guessing but problem could be your motherboard. Cheap mobos don't get full advantage of components and show poor performance (but they are advertised as "compatible", "supports"... whatever, but are not meant to be used for video applications). The video card is fine for gaming (though not great), but it makes no difference for versions you work with.