I have really expensive taste, so Im probably not the best for "what" to buy, but I know "how" to buy... as far as products go, there will always be opportunity to get better gear later on.
one thing i've learned is that there is no substitute for listening to speaker systems before you buy. take the time to shop, go to studios, and ask questions. there is a multitude of info on this forum and tons of guys/gals that are very knowledgeable.
whatever product you decide to go with, make sure that the company you buy from has a customer friendly return policy
I just will not buy anything unless I can put it in my house, run it for 15 days, and return it if i don't like it.
check out some of the other threads for technical information and how to set up your system.
the manufacturers that i have had success with are: Funk Audio, Epson, Samsung, KEF, JTR, Emotiva, CSS (for do it yourself stuff), Sony, Pioneer, Focal, and a few others in there. Denon was good sometimes, but not all the time.
Subwoofer recommendations: i would buy the 18.0C or the 18.1 by Funk Audio, i've heard them both and they are fantastic!! although Funk is regarded as more for the hardcore audiophile. i own a 18.0 and i know what the thing is capable of... Tintin on bluray in dts is killer. you can go with a JTR, good sub, honest company, but they lack in the looks department.
one thing that i missed learning about when i started getting into hifi was cables... you can spend truck loads of money on cables when there are better options than Monster cables. true, there is a difference in the quality of cables, but the equipment you are running can only transmit and receive so much information per second... so buy according to your gear. and to do that takes research and diligence.
as far as acoustics and sound goes, you are better off spending an extra grand on getting your media room nicely treated for sound performance... as one wise audiophile said "a speaker will only sound as good as the room it is in." ie: bad acoustics = bad sound, not matter what speaker you are running. i know this to be true, because i have heard some mediocre sound equipment sound fairly good when in a room with good acoustics, and when the conditions are that much better, you will be inclined to enjoy yourself that much more.
Best of luck and happy shopping