I have a feeling the 9500GT will slow you down. The 650 ti IS overkill for HTPC. So much so that I have one too(Wanted to be able to do some mid end gaming and for its low power use when watching videos)
If you are using Windows Media Center, I advise you to use the latest BETA drives as the current release driver seems to have the card spend lots of time at full clock speed and not reduced when watching video in Media Center.
See.
Image too big so click away. Top 3 current release driver bottom 3 are the new beta over about 1 hour of Media Center. It will still bump up from time to time(not shown in the chart, but I have been logging it. I don't want my media center to waste power when not gaming), but no longer stays at full speed most of the time with the beta driver.
http://imageshack.us/a/img211/3241/nvidiamediacenter.png
Yeah you will have NO power problems with that thing.