If changing the IR from 3x to 2x gave the desired performance, then you found your problem, the CPU isn't the issue. Lower that AA man, it's not like Wii games need so much anyways. Per Pixel lighting doesn't really give much of a visual enhancement to Brawl, so you could disable that too if you want, save your GPU the trouble.
To test your GPU limit, try having four controllers (hands) on the CSS, choose a character for all players, and open the Random Stage Switch from the top menu (In my experience, the most GPU heavy parts of Project M are the menus, especially the Character Selection Screen). Now increase the IR and AA until the frames start dropping. I don't know how high you'll be able to go, but don't be surprised if AA causes major slowdowns here, that's just how it is with this menu.
To test if your CPU can handle any kind of situation, activate all items at max, get four players to Skyloft or/and Delfino and see if it lags or if the frames drop. If your GPU didn't have a problem with the crazy CSS, you'll likely be fine here too. If not, lower the graphics settings.
Also, I really recommend you try this with Direct3D9. I think the reason you didn't get good results before was because you cranked up the AA too much.
To test your GPU limit, try having four controllers (hands) on the CSS, choose a character for all players, and open the Random Stage Switch from the top menu (In my experience, the most GPU heavy parts of Project M are the menus, especially the Character Selection Screen). Now increase the IR and AA until the frames start dropping. I don't know how high you'll be able to go, but don't be surprised if AA causes major slowdowns here, that's just how it is with this menu.
To test if your CPU can handle any kind of situation, activate all items at max, get four players to Skyloft or/and Delfino and see if it lags or if the frames drop. If your GPU didn't have a problem with the crazy CSS, you'll likely be fine here too. If not, lower the graphics settings.
Also, I really recommend you try this with Direct3D9. I think the reason you didn't get good results before was because you cranked up the AA too much.