The 9500 is not a good overclocker so I would not even bother. If it is for gaming it is probably not an upgrade but for running multithreaded applications or heavy multitasking it is. Just to give you an idea what to expect your 5000+ is running at 6000+ speed but the phenom is faster than the 9500 http://www.anandtech.com/bench/Product/28?vs=23
If you have both processors, why not give both a try?
If your board supports it, you can drop the Phenom in, and run some benchmarks or simple tests doing your everyday tasks. If you see a noticeable difference, you may as well keep the Phenom in the computer. If you don't see a difference, it's always nice to have a backup CPU around for troubleshooting.