Deep load testing

Hi all, I'm looking for a suitable load testing tool for a web app.

I need to hit the site first with a login (username, password, then submit the form), then adjust a few select list boxes, insert some dates into some text boxes, and then see how long it takes to get data back and displayed on the screen (via Ajax/JQuery I think). I'd like to test this for up to 500 concurrent users if feasible.

I already have a WATIN web crawler app I wrote which would be ideal, but it requires an instance of IE to be open for each thread, so that's not suitable as performance on the 'runner' machine becomes a problem.

So far I've tried:
-loadimpact.com, good but some bug stops the tests from running, I reported it.
-loadstorm.com, apparently not able to replicate form stuff.
-Apache JMeter, apparently not able to replicate form stuff too.
-FWPTT, simple enough, but crashes.

Can anyone suggest a tool, or a usage of the aformentioned ones to achieve this? TIA.

Hi Chockolate. Nice selection of tools! Have you heard about NeoLoad?
This piece of software is made for what you describe. Executing simultaneously hundreds of users submitting credentials and doing choices on a web app.
All web technologies included Ajax are handled: http://www.neotys.com/product/techno...ress-test.html. The learning curve is also quite short, everything being based on a powerful graphical interface.
A trial version is available on the Neotys website: http://www.neotys.com/product/download-neoload.html. Try it out and let us know your inputs!
Olivier Hanoun, Neotys Performance Engineer