I looked at each of the systems you linked to and only one looks like it might be decent.
- The Panasonic uses a single full-range driver for the front and rear speakers. Full-range drivers can sound good, but when a very cheap system uses small, full-range drivers that's a major red flag.
- The Sony uses tiny 3" "woofers" for the front speakers. Not good. That means the crossover between front and sub is going to be fairly high, which isn't very desirable. Also it doesn't come with an amp, so keep that in mind.
- Both LG systems didn't list any information about the drivers used in the speakers. That worries me. However, they did mention that the power rating for the amp is at 10% THD. Good amps/receivers are rated at .1% THD or even less, for comparison. So even though the LG amps are rated at 155x5 for the main channels, the amount of clean power they can deliver will be much lower.
- The Polk system, like the Sony, uses very small "woofers" in the front speakers and does not come with an amp. Also, for what it's worth, I have actually owned a Polk sub, the
PSW 12, and it was really disappointing. Below about 40 Hz output really dropped off leaving only port noise, the sound of which was remarkably similar to an F3 tornado. Suffice to say, that got returned. heh
- That leaves the Onkyo system. That system actually looks respectable. 5" woofers in the front should be able to go down reasonably low and the sub uses a solid 10" driver (and from what I've heard from other people, Onkyo subs in their HTIB systems are fairly decent). This system does not include an amp, however.
If you're going to choose one of these, I'd go for the Onk. At 260 it's already over-budget, though, and you'll still need an amp/receiver to power it.
That's my analysis of those setups. But let me also say that when I put together my current setup, I had the goal of spending as little money as possible while also getting quality equipment that would provide enjoyment for many, many years to come. I ended up spending about 450 dollars for the front speakers and sub, and I got an extremely good deal on the front speakers. I was frugal, but also willing to spend enough to get some legitimately nice equipment. My enjoyment when listening to music and watching movies has gone through the roof with this system. And let me also say that it's unbelievable what a true subwoofer can do and how much it adds to the experience.
So anyway, that's basically my story/perspective. Unfortunately, I really can't know what would be acceptable to you. While I might find the ~200 dollar HTIB systems a waste of time, they might suit you just fine. I suppose that's obvious, so I guess what I'm really trying to say is I hope this post helped you, but I'm not sure it did.

Edit: Clarity