Of course, I don't know exactly how much you spent, but you must have spent $2k or so for that Panny. Having an $800 budget for the sound seems inadequate.
Many HT enthusiasts (including me obviously
) see the audio investment being at least equal to the video one, and as you move up the ladder, costing more than the video equipment.
I understand you might have shot your wad on the flat screen and don't have a lot left. In that case, you could think about spending your $800 on a better front right-center-left set up or even a front right-left set up. Then you can add a center channel, sub, and surrounds later.
If I had a budget of $800, I'd get the best receiver and front main speakers I could, then use the phantom center setting on the receiver until I could afford a matching center. After the center, then I'd probably get the sub, and finally the matching surrounds.
If you spend $200 on the receiver, I assure you, two really good speakers for $600 will sound much better than five below-average speakers and a sub for $600. You'll have to be patient to build your system as you get the money, but at least you won't be thinking all the time that you wasted your money and have to start over because your inexpensive 5.1 system sounds like crap.
(In fact, if I were in your situation, I'd be looking at the used market to score some outstanding speakers at significant savings.)