New Car Purchase, Need Help! 2009 Nissan Altima 2.5 S 4dr Sedan (2.5L 4cyl CVT)

Guys,
I am in the market for a new car. This will be my first fully independent car purchase. I have test driven the following cars over the past 2.5 weeks (all 4cyl, primarily due to price):

2010 Ford Fusion: I had read a lot of good things about this car, but was not overly impressed with the drive or features. The 4cyl Fusion does not have all-wheel drive.
2009 Hyundai Sonata: Best price (with $3,000 cash rebate) and warranty, but drove like an old man's car. Interior nice, but not overly impressed. Exterior not overly pleasing. Not sure I could be happy driving this car for 10 years.
2009 Honda Insight: Was not impressed with the interior. And although unique, the drive was noisy and weak. Not sure gas mileage is that important to me. Dealer tried to sell the "hybrid" as a status symbol (right). Not sure now is the best time to invest in this type of hybrid either, given new technologies on the horizon.
2009 Honda Accord: I liked everything about this car, but it lacked "kick."
2009 Mazda 6: I liked this car. My runner-up pick.
2009 Nissan Altima: Loved the drive, great interior and exterior look. Only downside are the options.. they are bundled, which forces you to buy options you don't want. Higher bundles also require you to buy lower bundles.
2009 Nissan Sentra: Nice drive, but smaller car, which I'm not really looking for, but had to test drive it since I was so impressed with the Altima. It has some advantages such as better fuel economy, and at the same price as the base Altima 2.5 S, you can get a fully loaded Sentra. However, seems like a girl's car.

I am most impressed with the Nissa Altima 2.5 S 4dr Sedan (2.5L 4cyl CVT), priced at $21,540 MSRP / $20,195 Invoice, with $1,500 cash rebate this month (July 2009).

***?: Is it possible to get a new car for invoice or less, minus the cash rebate ontop of that? I have read about things such as "dealer cash" (incentive the factory gives dealers get for selling certain cars, which the dealer can either pass down to the customer or choose to pocket for themselves) and "holdback" (a percentage of the car’s MSRP that most manufacturers pay back to their dealers quarterly). This dealer claims Nissan does not do "dealer cash" but I have no way of verifying. I did not ask about "holdback;" I assume all dealers get this.

***?: Unavoidable fees I should expect? Destination charge of $720, title and license fee, etc..?

My '96 Ford Taurus does not qualify for the Cash for Clunkers program, but I believe I can utilize the Auto Assistance Ownership Amendment to write off the taxes.. just unsure precisely how to do so at this point and if I am able to at the full amount.

Any advice on negotiations from here? I am planning on trying my hand on some dealers in other cities first to gauge not only my ability to negotiate, but to see what the true market value is of this thing is.

I like the Mazda6 the most, but would get the Hyundai. Best Warranty out there at 5yr/60k. I got a Kia Spectra5 that has the same warranty and have had no probs yet, but I got it in December. Although, I look at cars as merely transportation.

Thanks, Dale. I liked the Mazda6 a lot, but not as much as the Altima. I think I'm pretty set on the Altima (though of course could change if some ridiculous rebate comes out next month).

Any tips on the negotiation side of things? Getting the best price on the car I want is my main concern, since I will be financing this thing by myself.