I'm in the midst of building a new Terminal Server. However, I wondering what CPU I should go with and it's between 2 AMD Opterons at this point.

The only difference I can see is the clock frequency and I wonder if the lower amount will hurt me in the end.

The Opteron 6128 is a 2.0GHz 8-core CPU
The Opteron 6134 is a 4.3GHz 8-core CPU

The difference is small but the price difference is $300 per CPU. If I go with the 6128, I'll save $600 which is very attractive, but will the power difference be noticeable? If the difference is noticeable, I have no difficulties spending the extra $600, but I have no interest in throwing that amount away if it wont make a difference in the end.

My current system runs a couple of Opteron 2220 2.8GHz and since the clock speed is much higher on these, will I actually decrease the performance by buying the new Opterons, even though I'll gain many more cores?