Buying a new HD Camcorder...help please.

[sjw]

Currently looking for a new digital camcorder to replace my (really) old Hi8 Sony.
Have now moved hi-def and have a 1080p TV and a PS3 too.
The current models seem to record in AVCHD so that's what I've been looking at.. And got rather confused with all of the model numbers (Canon and Pannys seem similar numbering.). Some of the camcorders record in 5.1 now. Just how good are the results (I do have home cinema set up) - can you actually hear a bias toward the rear channels if somebody speaks from behind camera?
Anyway, onto the main point of the post..
The first one I looked at the was the Panasonic HDC-SD100 and then saw that there was a HDD version - the HDC-HS100. Then it looks like that's been replaced with the 200 series - is this the same but with slightly bigger HDD and a touchscreen? There is also the HS20 and the SD20 but although saying they're 1920x1080 don't actually seem to offer 2M pixels? Are they basically the same as the 200 series (better than 100 series?) but with a smaller image sensor?
Then there's the Canon's. And the Sony's..
So, there's the Panasonics: SD20, HS20, SD100, HS100, SD200, HS200. What would the order be in terms of performance?
Canon have the HG10, HG20, HG21, HF10, HF110, HF100. What about their 'order'?
Sony seem more expensive and I'm struggling to tell which models are 'current'.
I assume the pictures are captured as mts files which I can copy directly from the camera to either the PS3 or PC and could either play them there or 'downgrade' them and burn to DVD at DVD resolution or even as data discs where the PS3 could play them too?
Lots of questions there and I really would appreciate some help and advice on this - where models fall within the ranges - or even all together..
I didn't really want ot go above £700 but am wondering if I'm getting lulled in by the HDD sizes and would be fine with a couple of big SDHC cards - or wouldn't I save much? Also, any good deals at the minute - and considering all the online places selling these things and mindful of not getting an import, any places to avoid?
Thanks for reading and hope you can help.

Steve