Cart before the horse or horse before the cart?


So, I'm finally building my first home theater and just purchased the TV, (LG PK950)so far very happy with my purchase.

My question is, if you were going to be starting with nothing, would you buy your receiver first based on your needs and then the speakers, or would you buy the speakers first and buy your receiver that best compliments your speakers? I've read so much about different receivers better suited for different speakers.

I'm undecided on speakers at this point, but I know I'm going to be buying used, betting I can get better quality for my money.

Paradigm Studio 20's or 40's
PSB GB1
Usher S-520
Energy RC10
B&W 6 series, etc.

Reciever: Not sure at this point, Onkyo, NAD, Marantz, Denon...

Honestly, there are so many opinions and when I think I've got it figured out something else comes up...need a little help please.

Budget:
speakers $500-$600 (used bookshelves)
receiver $700 max

For now, just the two bookshelves and receiver.

System dedicated to mostly HT and some music, IPOD and vinyl, punk and garage.

What do I purchase first? Thanks everyone.
dufrain
Something similar to a Pioneer VSX-1120-K would be a great unit as it's very current with the latest technology.
I don't currently own a receiver or speakers...recently moved to another city and now am starting from scratch. I've been looking at the Onkyo line of receivers, 608, 707, and 806...haven't thought of pioneer I'll have to check them out, Thank you.

So, it sounds to me like I should purchase the receiver first based on my current and future needs?
Speakers first. Because they might be 4 ohms, and then you need a receiver that is good into 4 ohms.
I got a set of Canton new 300's (4) and 360's (3) at 30% of retail at a blowout/closeout dealer sale. (still in the boxes and yes that is 30% OF retail, not 30% off)
I got a nice demo Denon 4806 at the same sale, half off.
I am certain I will never bother to upgrade the speakers, I like them very much.
For the speakers, I've pretty much narrowed down my search to Paradigm Studio 20's or 40's, whichever I can find for the best deal on used, PSB GB1, and Totem Rainmaker.

Any recommendations for a receiver? I guess I've been leaning towards the Onkyo line (608, 707, 806) because of all the features and I can get at a very good price from a certain online dealer..(don't know if we can name dealers on this site).

Mceljo recommended the Pioneer VSX 1120 K and that seems like a nice choice...any others I should look into?
I know I should audition all of this, but the closest dealer to me is 2 hours away and they only have the paradigm.