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
Post removed 
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.
If you're not wanting the option of pre-outs to step in the future to a 2 channel amplifier then you can drop several levels down in that same line and get a VSX 820 that should have plenty of features for less money. A friend of mine recently purchased this model for his 2nd system. He uses a Pioneer Elite model in his home theater room and used the 820 to run the rest of the speakers in his house.

Onkyo and Denon are also great options, I prefer Onkyo over Denon simply because they are a bit more user friendly with individual buttons on the front rather than a spin selector knob.

In my opinion, the two most limiting features in a receiver in the long run is not having pre-outs or 4 ohm capability. Both of these features add to the cost so you need to figure out how much it matters to you.

I also don't think that in the price range you're looking at that matching speaker and receivers is as critical as it obviously is in the higher end gear. I don't think the difference between a Marantz, Denon, Onkyo or Pioneer will make a significant difference with any speakers you'll be considering.
Onkyo TX-NR808 would be a great option from the online retailer that you speak of. A co-worker of mine just purchased one and seems very happy with it.

It is rated for 4 ohms and has pre-outs. The current price is right in your range.