Ok here is my personal opinion.... the DLPs are very nice sets and a fanstastic choice. I think youd have to be insane to buy these things online however, especially since most places arent authorized retailers. I'm unsure about Samsung, but I know alot of companies like Pioneer and Sony refuse to warranty their TVs from a non-authorized retailer. And then toss in the fact if something is wrong when you get it, you dont have a store to go to and swap it out easily. Not to mention currently the NEW DLPs are more expensive online then through CC or such, like CC currently has the new HLP4663W for 2849 where as online best price is 3174 that I have seen. And I'd recomend the new DLPs over the old ones, like the new 63W series... it uses the newer HD3 chip, which has a higher contrast the the older 7W series (617W, 507W etc..) and it has a 7 color color wheel instead of 6 like the old one. The new 63 series also has both HDMI and DVI. As for the warranty.... I personally think it is worth it but I use my TV alot, I would probably go through 2 bulbs, you just need to make sure it covers the bulb (Only CC and Sears cover the bulb AFAIK, I know BB doesnt nor does Fry's, Ultimate Electronics, or Tweeter.
As for cables.... dont use cheap cables like radioshack or GE, Monster cables are very good, but yes they are overpriced, it is nice you know their good, but you can find good cables cheaper however online just need to make sure their not crap cables claiming their good. For people who say crap radioshack/GE etc.. cables are just as good as higher end cables and youd notice no difference.... I think their nuts, there is a deffinte difference.
Also if you dont have Digital/HD right now and you have comcast analog... you can get better deals by signing up in stores over just calling Comcast... if you switch from analog to digital/HD at CC you get $100 off your cable bill (basically 2 months free) or with BB you get a $50 MIR... I went with the $100 at CC.