Rob,
I expect Joe from The Media Factory will post here later, but if you like detail, you can download the combined 433/503 user manual here...
http://www.attbites.com/stuff/503_v2.pdf
I've just ordered the 433 MXE from Joe and he's been a great help so far.
I've not seen the MXEs but have seen both the HDE models though not side-by-side. Spec-wise I think the 503MXE has about 10% lower peak brightness and contrast ratio than the 433MXE. They both come with identical scaler/ video cards (PDS-5002) which are upgradeable (there are rumours both here and in the US of new cards from 3rd parties later this year. Joe can tell you more).
Check out the US
www.avsforum.com if you haven't already. The models there are identical except they are called the CMX rather than MXE. The 503CMX is very popular but there are several regular posters with the 433CMX too (try searches on users Jim Boden and GGoodrum respectively).
My decision came down to a compromise - as always - the 503's true WXGA would be great but 50" is a bit too big for my lounge and I can buy a lot with the spare £2200.
If looks are important, note that you can now get the 503 in both silver and charcoal frames (with no price difference) whereas the 433 is only in charcoal (you can remove the bezel and respray it yourself if you're feeling brave).
Finally, you probably won't get a better deal on a 42"/43" XGA plasma for a while. The new NEC MP4 is floating around the £4600 - 5100 mark and the new Panny 5 (XGA) isn't due til november and I can't see it being priced below £4000 either.#
Happy shopping,
Phil
