Portfolio Model Programs

I am looking for either a website or software that will allow me to test different portfolios over time. Essentially i want it to tell me annual income based on holdings and show me the performance of the portfolio over a ten year period. I would also like it to be able to compare three different portfolios so I can see which one performed better. I don't know if there is a free one online or if it is something I may have to pay for and download which is fine as long as it accomplishes these tasks. Any suggestions would be appreciated.

available on Vanguard.com

kwanti.com is awesome for this type of analysis. I am not sure how much it cost because my firm pays for it.