Will I see a great benefit with certain Onkyo receivers paired with these speakers.

You will probably be satisfied with the 605, but the 705 or 805 may be a better choice depending on how loud your listening levels are (I watch movies at reference level) and how big your room is.

I watch movies on the Onkyo 605 at about 61-62 level. I don't know what it goes up to, but if I listen to it any more then that it gets annoying. Not that it sounds bad, it sounds just fine at higher levels, its just too loud and it wears me out quick.

The 340SEs + 170SE speakers will be the SQ limiting factor with any of the AVRs that you mentioned.

If power and sound quality are your only basis for comparison I'd remove the 705, it's going to be more of a sideways move from the 605 in that regard, it's biggest features are the added preouts and extra HDMI input.

I think you'd notice enough of a difference between the 605 and 805 to justify the price difference which is becoming less and less with sales lately. Especially if you listen at higher volumes, the weight difference between the two is a good indication of the difference in the amps and heatsinks. The 805 is a tank in comparison.

From what you explained, I think that you would be more then satisfied with the 605, especially for the price. Onkyos make really good receivers, and from what I have heard from the 605 so far, it sounds REALLY good. Sounds even better then my Onkyo HTR-510 receiver that I have had for about 3-4 years, I can especially tell in the surrounds.