dont buy an hd dvd player, they are about as useful as VCRs because blu-ray replaced them. and if your going to buy sony stuff buy their individual speakers and receivers , way better then their all in ones, ive heard a few of them and they suck terribly. or better yet buy monitor bookshelfs from polk, you can get them at newegg.com for 100 a pair total of 420 for the fronts, back, center, and sub (get a polk monitor sub at newegg for 119). i personally have yet to hear an all in one system at the price of 500 or below that is even worth considering. stay away from sony subwoofers as well, they are no good. your not going to get a usable receiver for less then 300 either. hopefully someone else here knows of a decent all in one for 500.
keep in mind that even though i mentioned sonys speakers does not mean they are the greatest thing out there, they are just decent, stay away from their 2-way bookshelfs for the fronts, they arent very good. polk is honestly a better choice. you could also look into some Behringer b2030p's, (note: do not get b2030a's) i personally have never heard them, but almost everyone on here likes them.