Between the Infinity & Aperion systems you list, I'd WAY go with the Infinity. Another to take a look at would be an Onkyo system - they have good "bang for the buck".
Stick to your guns with your budget & full 5.1 system. For budget, there's always something better & more expensive. For 5.1, if what you listed for your goal was kicking back to music, I might lean towards a nicer stereo pair; but you said 55% games - get 5.1, you can always upgrade bits & pieces as needed.