I was a commissioned salesperson in a previous life too. LOL! Consumer electronics for me. Vendor spiffs went directly to our paychecks in my case.
I agree with akirby on dealing with a sales manager especially if you know exactly what you're looking for. As for my most recent purchasing experience, I was able to negotiate $6,000 off of a 2009 Audi A3. $2,000 of it was from factory marketing support. Other factors that worked in my favor included the fact that it was near the end of the 2009 model year, that I wasn't deadset about color and some other features, and most importantly I dealt with a sales manager that was no nonsense but helpful. I ended up emailing him and from his very first response he gave me the option of 1) any 2010 on the lot for $200 over invoice or 2) negotiating for one of the 2009s with the $2,000 in marketing support. Within 2 or 3 more emails, we were able to agree on an additional $4,000 off which translated to a bit less than $4,000 below invoice. All the negotiation was done via email and all I had to do was spend an hour at the dealership test driving the car (since I hadn't driven that specific car yet) and signing the paperwork. One of the most important things that happened was that I let him know when I gave him my final offer that if he gave me that price, I would be in later that evening to pick it up.
Another great way to get a deal is to get the car that's in the ad. There was a time that these cars sold really quickly but that's not necessarily the case anymore. The disadvantage of this, of course, is that you don't really have much of a choice in color, equipment level, etc. The upside is that you can sometimes get a car with more equipment than you really wanted at an even lower price.
In regards to your comment about having a bad taste in your mouth about car sales, you shouldn't feel that way at all. It's pretty obvious you do your research. If anything, armed with the info that you have, you should actually relish going to the dealership. The key is remembering that you ultimately have the greatest power - you don't have to buy if you don't want or if you feel uncomfortable. And if you don't like the person you're dealing with, you can find someone else. Car buying can be fun especially when you show them that you've done your homework and that they're going to have a hard time putting one over on you. It really changes the way the salesperson treats you when that happens. If you can, make sure you go to the dealership with a level-headed friend or family member. They can help you keep a balanced approach and deflect any pressure the salespeople might try to put on you.
Good luck to you in your search!