Depends on what you are hoping to achieve with your system.
I've learned, after spending a bundle on "upgrades", that it is better to wait and save than to go the upgrade route. You always wind up spending far more than by waiting and saving for the speakers you really want.
Were it me in your position and had to go the upgrade route I'd buy speakers that would move to the "surround" position, or in another room.
For instance, as a Paradigm fanboy, I'd buy a pair of Atoms to go with the receiver and when I had enough saved I'd buy the fronts I really want...in your budget and listening needs of course...and move the Atoms to the surrounds...hmmm that is actually what I did. I started with a pair of Atoms then a pair of Titans...daughter has them...then a pair of Monitor 3's...son has them...now a pair a Monitor 11.s...the final step...until I start to move to the Studio line if I am so inclined.
Over a period of time I put together a very nice 5.1 system and made use of my "replaced" speakers.
I use the Atoms as surrounds, rather than the Titans or Monitor 3's, because of the dreaded "wife approval factor".
Regarding the receiver. You may find the Pioneer line to have a very nice selection of receivers that are within your budget range and according to reviews, in magazines and podcasts, sound very good as well.
Good luck and keep us informed.
TV: Samsung 60KS8000, Rcvr: Marantz SR5011, Speakers: front/Paradigm Monitor 11v5, center/Paradigm CC-290, surround/Paradigm Atom, sub/Paradigm PDR-100, DVD: Samsung BD-J5700, Remote: Logitech Harmony Ultimate Home