Those are pretty efficient speakers. So you will not need a lot of power to make them loud. And by buying a receiver that has major amount of power, would be overkill. You do have a decent budget for a good entry level receiver. I would recommend mine. I got it for 393.00 shipped. But at 125 watts x 7 channels it is more than you need. And a tad over budget.
Are there any features that are a must have for the receiver?
Do you plan on any upgrades in the future?
Is this going to be strictly hooked up to the computer, and not used with a big screen tv? Meaning will you need component upconversion. (I am assuming not)
I believe the Pioneer VSX-815 might be a decent choice. Which can be picked up for about 240.00 It has all the latest decoders. 100 watts x 7. Also has MCACC (Automatic calibration)
The MSRP is 365.00 but can be had for much cheaper new. About 240.00 here is a link straight to Pioneer for this receiver.
http://www.pioneerelectronics.com/pna/product/detail/0,,2076_4153_209695979,00.html
The Yamaha HTR-5750 is not a bad choice at all. But it only offers 6.1 and less wattage (less total wattage). However if you have no plans to upgrade then this as well may be the one for you. Considering its about the same target price as the 815