@Trix, I haven't done much research as to where I am going to buy my TV, but Tafelberg Furnatures comes to mind. They generally have really good prices, are willing to negotiate and I'd think that they offer extended warrenties. Negotiating free delivery is a good option too.
I might get the TV at Frontosa (PC wholesaler - don't sell to the public) for around 20k (perhaps less), but I seriously doubt they'll be able to offer an extended warrenty, so I might have to shop around as well.
For me the extended warrenty is a must!
But please do let me know where you decide to buy the TV and what the experience was like.
Those models you mentioned - I popped in at Hifi Corp at Canal Walk at the Boulevard shopping complex on the edge of CW and saw them there as well. Can't recall any prices though, but worth a shot.
I also believe that Ster Furnatures are also negotiable too.
Time to get on the phone and call 'em all up.
Just to update you. My PS50B650 arrived yesterday.
I'll start you off with the bad first.
1) There is no optical audio output like there is in the American / European version. You have to make do with normal Audio out.
2) No Video out (Any types of video out)(I need this for my old LG DVD recorder)
3) The remote is as long as my forearm and not very good looking.
4) I wish I had gone for a bigger model
As you can see, not much bad

, now the good.
This TV is fantastic. The standard definition via my SD PVR is terrific. I expected to be good but not this good. The only DSTV channel that looks bad is Trace TV. It has tons of inputs as well. I plugged in my hard drive and it pretty much plays everything, even of a NTFS drive. I also have no buzzing as yet. Also can't say anything about IR as I was constantly changing channels

.
The internet functionality wasn't as sluggish as mentioned. Only have two widgets for some reason though, Weather and Youtube. Both work pretty well though. Will try and install more later today. I haven't even tried the DLNA functionality yet. Didn't want to wast my time starting up the laptop.
I would really love to test a B550 now and check the differences. I am sure that the picture engine on the B650 really helps the SD content and therefore is worth the extra money. That as well as the internet / DLNA features and the ability to play movies of a hard drive etc. It also looks better than the 550 with the glass over the bevel and the glass over the stand. The stand also has a glass stalk and the buttons are touch sensitive not that you'll ever need it.
Overall, I love it and I only played with it for a couple of hours. I can see why it was rated the no 1 50 inch plasma on consumer reports. (In terms of functionality vs affordability vs picture quality)
Also, Any Samsung TV purchased from now to December will carry a 3 year warranty. So got my TV + 3 years warranty for 21.5 K and paid another 2K for an extra two years. On second though I probably shouldn't have taken the extra two years but I already did the deal when I ordered so wasn't going to back down from it.
If you need any other info, just let me know...