Dsharp, since you can only deal with optical, I would get a used or refurbished AVR that has a optical input off of ebay or craigslist or something like that, and get a pair decent bookshelf monitors.
Here is a system with new components only that I think would work well for you: Behringer 2031p monitors (
$233 shipped here) with a Harman/Kardon 3490 stereo receiver (
$310 shipped here). Those speakers have very good bass for bookshelf speakers, as well they should with 8.75" woofers, something to think about since you are going without a sub. The only problem with that system is it can not be upgraded to a surround sound system if you should ever want one, since the receiver only does stereo and the speakers are 4 ohm speakers, which most entry to mid level AVRs do not handle well.
A good alternative would be some
Hsu HB-1 bookshelf speakers ($306 pair shipped), with a Yamaha RX-V467 receiver (
$215 shipped here), that would leave room to grow if you wanted to expand out to a surround sound system. The Hsu speakers also have terrific bass for bookshelf speakers, as they should since Dr. Hsu is the subwoofer expert. The speakers are a bit more expensive but will work well with lower end receivers, and they sound great as well.
Also to Sholling, for Infinity Primus speakers there is no reason to go with p163 over p162, unless you really love that black grill. Functionally there is no difference, but you can get the p162 for $85 shipped each from Crutchfield. However if I were going without a subwoofer, I would go with the Behringers or Hsus, they have stronger bass than the Primus bookshelf speakers, and you would want as much bass as you can possibly get in that situation.