Stuttering audio almost always indicates an insufficient performance of hardware, or memory. This also depends much on the audio source, and the software used.
In case you have no sound issues on your host Ubuntu different Pulse Audio settings will not do much about sound issues arising from running a quite demanding guest OS like Windows 7.
To minimize effects coming from limitations of a virtual machine we therefore have to make sure to assign as much hardware ressources to the guest OS as possible, but make sure the host OS is still able to perform well (including Pulse Audio in your case!).
From what we can see from your settings it seems that the requirements to get a smooth audio experience are met. There are few things only we may try to see whether there is an improvement:
- assign 2 of 3 CPU cores without an execution cap (or 3 of 3 but then with an execution cap)
- give the guest OS more RAM (e.g. 3 GB of 4 GB)
- assign 256 MB of graphics RAM.
In case we then have a better sound output we may reduce the ressources step by step to find the optimum setting for the software we run on our guest.
If we still cant get sound output smoothly we may have to try using a software with less demanding sound processing like e.g. WinAmp or Foobar2000 to further track the issue down.
It may however be that your hardware capabilities - even though quite good - still are inssufficient for running Windows 7 and your additional software to play sound (and video?) at the same time.