Currently, yes that is the best. The GTX 950 has recently been announced, but as of now there are no low profile versions of it as far as I know. Just because that is the best doesn't mean it will work in your system though. Your PC has a PCI-E slot that can only supply a max of 40W, which isn't enough for even the very lowest of current GPUs (The R7 240 from AMD, or the GT 740 from Nvidia.).
The best card that you will be able to run is a GT 730 (The 64-bit version, not the 128-bit) or an HD 6670.
If you have any further questions, please consider starting a new thread (And posting the link below so that I can help you out as well.) since you won't get many answers if you post on old threads.