If they sound good to you, then you didn't screw up. Don't second guess yourself and just enjoy them. But definitely get a good sub to go along with them. I like Hsu (because I own one), but have heard good things about SVS, too. I have a cheaper Polk sub in another room (didn't need anything fancy), and it just doesn't compare. You will be much, much happier with a good sub.
Panasonic TC-P60ST60, Pioneer SC-1523-K, Oppo BDP-103D, Pioneer PL-550 + Cambridge Audio Azur 640P, B&W CM1 (fronts), B&W CM Centre, Wharfedale WH-2 (rears)