I would not buy a maxima new because their depreciation is ghastly. It will drop in resale with a quickness that blindsides you and makes you wonder if you've stepped into the twilight zone.
Of course that Audi will be an absolute dog when compared to the maxima in terms of performance. Maybe it will handle better, but who cares it's got almost 100 extra less horsepower. Those things aren't rockets in the first place, especially with drivetrain loss. I would buy the maxima. Except I wouldn't buy a new one (resale).
The g35 awd is a good recommendation. If power is of importance to you drive both a g35 and a maxima, and then the audi. Then you'll drop the audi off the list immediately. Slow as hell unless you'll chip it, and then it still will lose.
OK you're obviously caught up with the image of some of these cars. I'd invite you to drive the 325i. It's another dog-slow piece of sh*t. Better interior and handling than the maxima, but slow as all hell for acceleration/highway cruising, etc. You're paying in great part for the BMW badge.
Take these cars out for a drive. Only then can you really make a decision. I have to say, though, that I drove a late model 325i a few months ago and was thoroughly underwhelmed for what the high sticker price buys you. Hell, why not buy a mazda rx8? Faster than all of these and prices start at $27k. If concerned about reliability get an extended warranty.