On a stock cooler I would think that you could get to 3.6 if you have a good chip for OCing. If not 3.4 should work. If you are planning on an OC it is just better to get another cooler.
To clairify what jonny said, On the 550TI you should be be able to raise the core clock, memory clock and the shader clock up in small increments. Test or stability each time you bump the clock. Find the maximum of each individual part before moving to the next. (so find max core clock, then find max memory clock , then shaders.) If you do see artifacts, take down the clock 10-20MHz and call it good for current part you are OCing (core/memory/shaders). Then move to the next. Be sure to look at the temperatures to make sure that you are not getting too hot.
MSI Afterburner does offer Voltage adjustments for some of the GPUs. If you are comfortable with that, increase the voltage slightly when the OC is unstable.