Hi,
RME would be a right choice..You will notice the improvement so much. I use M-audio 2496, latency is around 6 ms..Pretty solid drivers..However, when it comes to the mixing while using plugin effects, it is not as good as professional cards..RME is one of the professional audio interfaces. Another one is Lynx. I am thinking about moving to RME, too.
By the way, DSP means digital signal processing. Such those cards take the load of plugins and effects (like reverb, compression, eq, etc..) from PC during audio processing. So, PC doesnt use its CPU power for realtime processing, therefore host audio programme runs smoothly without any click or drop.
Take care..