The bottom line is the
difference in sound between your extremely nice gear and a $500 receiver will be subtle compared to the tremendous differences between well designed and poorly designed speakers.
A $500 receiver from any major brand is designed using well established approaches to control and amplify (while maintaining) the original signal. It is a mature science and can be done well without any great expense. The advantages of high dollar gear are usually design refinements which may or may not be audible.
However, as soon as you listen to any two different speakers you are pretty much guaranteed to hear a very obvious difference. There are some expensive speakers that sound pretty poor and some inexpensive speakers that sound pretty great.
If I were you, I would:
1) Buy a pair of Affordable Accuracy Monitor speakers for $200. This will give you familiarity with the sound of a good and accurate speaker which will help you when you go out and listen (if you are like most people, you are simply not used to hearing quality sound reproduction).
It will also give you something to listen to so you won't get impatient and go for the "today-only special" when you should be learning enough to better use your limited funds.
http://philharmonicaudio.com/aa.html
2) Check out Audiogon on-line. It is a classified service for high end audio gear.
3) Decide how you will get bass for your system - do you plan to use a subwoofer or use full-range speakers.
4) Keep asking questions here.
BTW, I don't understand the issue about sensitive speakers and hiss. I suppose if you have the notion that a measure of the quality of your system is to turn the volume all of the way up when nothing is playing to see how much hiss there is, a sensitive speaker could do poorly, but that is because it is essentially being played much louder. At equal volume levels in your room, there should be no difference in the amount of hiss due to sensitivity. The only difference in hiss at equal volume should be due to a frequency response that emphasizes the hiss.