Alright, I keep forgetting to ask this question with people but where are you located or perhaps more importantly, where can you buy from?
I ask because I really only find search pages for the LG in India.
First thing I'll mention is that on the PC, not all applications will do surround, they will be stereo only. If you plan of watching movies from disk, this is probably where that's important and want to pay attention to what you are using for playback. Unfortunately, this is something I'm lacking in knowledge about as I use stand alone players. Perhaps someone else can help with that if you need it. Apps like Netflix/hulu/etc should support surround playback though.
Also, how do you connect to your monitor, is it via HDMI?
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Right now, with your list the Logitech will be the only one that will work with what you have since you can use the 3.5mm jacks.
Any system where you have to connect via spdif (optical or coax which the other two on your list would need) you will have to transmit DD or DTS to get surround. This means you'll need a soundcard that includes Dolby Digital Live or DTS connect where the sound card does the encoding, or I believe there are stand alone software out there where you can use your cpu to do the encoding.
The unfortunate part is that not all all-in-one HT systems will decode DD or DTS over spdif and I haven't found anything that says one way or the other with the LG or Philips so I cannot guarantee you'll have surround with them.
So, back to the question of using HDMI, if you are then I have another option if you are buying in the US:
Monoprice 5.1 HT system #10565 (out of stock til April though)
with a refurbished Denon AVR-S500BT from Accessories4Less (get at least the 2yr extended warranty with it)
This puts you around $370, I believe both sites have the option of ground shipping so maybe around $20 for that so you'll be at $390. That leaves wiring, you can get a 6ft subwoofer cable for $1.50 and get the 14AWG Select series speaker wire for $12 at Monoprice.
It's over by a tiny bit, but it's a better setup than than any of the systems you listed.
But if you want to stick to the ones you listed, my first choice would be the Logitech as it's the safer choice and should sound as good as the other two choices.