If you are anything like me and concerned with quality of sound I can HIGHLY recommend the COBB exhaust. It is not annoying or too loud and is acceptable in every way to me. I have owned race cars as well as heard MANY different exhausts over the years on WRX and STi models and 90% of them to me were too loud and annoying.
I am down in Lake County quite often and on Thursday night's for the Lake County meets and would be more than happy to let you hear the COBB on my 08... I know it's not the Invidia but I think the people chiming in with how loud the Invidia is offers some insight that you might want to consider something quieter.
Hope this helps and good luck either way!