Looking for the best option available to automate

I have a couple of options and directions I am looking at to come up with a solution to automate the functional testing.

Current Process: Currently we have been using the soap UI to manually set up the test data and verify the Web Service response manually, Since each functional test case has
a very different situation to address, this has been working fine for us over the years. Now on the negative side this has been a very intensive process to set up data each time we execute test case (as the wsdl changes frequently). I am now looking forward to reduce the burden of testers.

Options I am looking forward:
*Using HttpClient open source f/w to set up a generic client and use XMLUnit to validate the response and integrate these two with Junit , this will help me to counter the ever changing wsdl, on the negative side , somebody would need to maintain the java based integration. Also possible to make these data driven using Excel based OS frameworks.

*Using SOAPUi automation.

Any evaluation of the above and comments are welcome and I would also appreciate any good solution for the above.

Thanks,
Amit