Consider simplicity of use to you and others that may access your system. Plenty of remotes are a sure fire way of confusion and stuff not working. Are you a music lover? Are movies your thing? What sound do you expect with the picture in the long run? I would suggest that you get speakers from strictly a speaker company. It hard to go wrong when it is what they do for a living. Onkyo makes very good amps and receivers, speakers are not a strong suit for the money.
Energy makes the V Minibook shelf speaker $225 for a pair
http://www.energy-speakers.com/na-en/products/v-mini-overview/
ESW C8 Subwoofer is a better buy in my opinion compared to the 10 inch dow firing sub at the same price. If you are looking for sound with small but mighty speakers, forward firing subs will better compliment the sound in the room. Down firing subs push sound down to the ground and up, not out. Doesn't make much sense to me, someone knows more than I do on that one.
http://www.energy-speakers.com/na-en/products/esw-c8-overview/
If you purchase a nice set of speaker stands, or get a set for Christmas, you will have a nice complement to your plasma screen tv. If you do not have a receiver then that would be another set of choices.
To avoid the cost of a receiver I would encourage self powered speakers can plug and play. Audioengine and M-Audio are great options. In this case speaker stands. M-Audio speakers take care of the subwoofer component built into the speakers at a reasonable price.
http://www.m-audio.com/products/en_us/MAudioAV40.html
Audioengine A5 hold their own and then some.
http://audioengineusa.com/Store/Audioengine-5
Nice little amp, though you already have an amp in the A5 but the music just gets better.
http://audioengineusa.com/Store/Audioengine-N22
High quality self powered units within your budget.
Happy Holidays.