My experience with the same syndrome...
Agonized for weeks and finally pulled the trigger on a 54G10 from Ultimate Electronics. Great experience at the store, they wheeled and dealed for my business, price matched a sears deal they didn't have to, threw in a blu ray player, etc., etc. Was sure it was the television I wanted... until the hamster wheel in my head kicked in.
So then I went to BB (a place I swore I'd never go back to after horrific customer service experiences) and kicked around the notion of trading even for a 58S1, beat up the sales people until they did better on the deal even than Ultimate had, and pulled the trigger. Passed on the free delivery so I could get it home faster, and set up both screens in the living room to see which one would win the Battle Royale. This is just smart consumerism, I tell myself. I'm inhome auditioning, which anyone with a brain should do with a purchase this big, I assure myself. You're not out of control with this, as you have been with every other purchase you ever make.
S1 dead as a doornail, nothing but a loud whirring buuzzzzzzzz when I turned it on. I call BB to come and get it, and they tell me "No sir, we would if we had delivered it, but we didn't, so you are on your own." I figure the fates are telling me something, and that I should just return it and be happy with the G10 like I had been in the first place. So I box up the mother, borrow the van again, and take it to BB to return it. I'm even keeping the PS3 they threw in at full price as penance. So the manager asks why I'm returning, I tell her it was broken out of the box and I just want my money back, and she works hard to keep my business when she hears that it was faulty and I was just going to return it. After much haggling, and much inner turmoil on my part because I had told myself that I was just going to return it, she offers $400 additional off the price and the free PS3 to boot if I'll just take another one in exchange. My head says "no no no no no" and my mouth says, "Ok."
As they process the exchange, Geek Squad opens the box and (this is where Karma and Fate intervene) sees a HUGE crack across the screen that absolutely was not there during any of my close inspection, and should not have happened during my extremely careful boxing and handling back to the store. Manager asked me if it was cracked when I opened it initially, and I say not that I noticed. She goes on to explain that this changes things and now I am looking at a damaged item which is not their problem, and not only does the $400 evaporate, but so does the exchange. I say, "what if I'd said it was cracked when I opened it?" and she says that she'd still do the exchange as we'd agreed in that instance. I was honest, and am being punished for it, typical with my experience at BB. So I'm now the proud owner of a busted 58S1 and may or may not have recourse with Panasonic, but probably not because the warranty doesn't cover cracks.
I'm not one to sit still for that kind of thing, so after a fair amount of haraunging, they exchange the set - minus the $400. I go through the whole process again, take it home, and leave it sit while I stew and get yelled at by the missus for another debacle like so many in the past with this type of thing. I'm out $3000+ on the credit card while figuring it all out. Should I return it to a different BB? Will I be able to? Should I return the G10 now, and keep the S1? What about the poor treatment I received at BB? Who pays for that? And why did I create the freaking mess in the first place???
Final analysis? I go back to the same BB, talk to someone else about the issue, and get them to honor the offer of additional compensation (now only $250, it's as high as I can get them) for basically calling me a liar. Of course, I had entered thinking I was just going to demand that they accept a full return. I feel dirty and used walking out of there, as I have so many times before. I skulk back to Ultimate Electronics and return the G10 and bluray player trying hard not to run into possibly the nicest and most helpful salesperson I've ever met while ripping his commission away from him with the return. I got the 58S1 for a significant savings from any sale prices, but I went through endless pain to do it, and gave up a tv I was immensely happy with in the process.
And then I spend countless hours here trying to satisfy myself that I did the right thing, attempting to replicate the THX mode with SM tweaks, purchasing a DVI to HDMI adapter to get back the pc input I lost off the G10, and hardwiring ethernet to the PS3 to overcome the loss of networking. Am I happy?
Shoot, I don't know. But I do wish that I could just relax and live with my decisions when I make them, instead of running the same circles you are clearly running. Not sure if this helps you with your problem, but sometimes isn't it nice to know you share it?