I am very particular with the quality of the audio/video when I watch movies and TV Shows dude. It has to be perfect. That said - I cannot fault my GT210. I am running the GT210 with a stock HPMS setup. 2GB RAM.
I would however rather spend a little more and get the GT520. Mainly because I wanted more functionality out of my HPMS. My projector is 3D capable but requires nVidia 3D Vision. I also want to and rips (got a bluray ROM in the HPMS) directly on the HPMS and the GT210 does not aid here (in my case anyway). The GT520 has Cuda and 3D Vision so much better value IMO.
I originally went for the GT210 because it served my immediate needs. Not even a month later and I forked out for the GT520 as my needs increased. So ye dude - fork out the little bit more and go straight to GT520.
To give you an idea on converting using Cuda.
I was doing an MKV to MP4 conversion using Xillisoft. Xillisoft supports Cuda if it is present. With the GT210 it is not so the rip was done the good old fashioned way using the CPU. The 1080p conversion took 4 hours and 12 mins on the HPMS.
I then did the same thing with my desktop which has a GTX560 and supports Cuda. The conversion took 14 minutes. While my desktop is more powerful than the HPMS, I have no doubt in my mind that Cuda aided a LOT with the increase in speed.
I also stream from my HPMS to multiple Plex Clients and DLNA Clients. Where the client cannot handle the codecs, the HTMS will transcode. I am pretty sure a Cuda based card will relieve the CPU of the transcoding but still need to test this. I hope it is the case.
When I put the GT520 in my HPMS on Sat I will re-run the 1080p conversion so we can get a direct - on the same box - comparison of pre/post Cuda conversions.
Hope this helps with your decision dude