Upgrading my current onkyo SR-800

[gochumonster]

I bought an onkyo SR-800 about 6 months ago and i am happy with it, but i really want to upgrade my audio setup, i can only afford to do it pieces at a time though. Do you guys recommend i go straight for a new reciever, say the 605, or should i replace speakers first? It seems like the speakers that came with the sr-800 are pretty decent speakers, but i still think i could get better sound then i am.

I currently have a ps3 that i am running audio out on the optical port, and i really want true 7.1 sound, but to do that i have to upgrade the reciever. So is it better to upgrade the reciever first and then start replacing speakers, or should i get a new center channel speaker, and satelites down the road, and then get a reciever later? Any help from the audiophiles out here would be appreciated. I wouldnt say i have a small budget just not a big enough budget to go out and spend $2,000 or so all in one shot.