Yeah, avoid those. There's a reason people still buy from B&H online.....
Anyway, you'll obviously get better photos with a better lens, but usually the difference is only slight. If you're into photography, that slight difference may be a very big deal to you. For yourself, I'm guessing you won't even notice the difference unless someone at this forum pointed it out to you.
The Pentax you're looking at is going to take some great photos for you, as long as you get better at photography and take some interesting photos with it. Kit lenses are usually cheap, but they're honestly capable of taking great photos. In fact, you won't even know you were using a cheap lens until someone tells you. It's just that sometimes these lenses may have trouble with a certain type of lighting, or they'll result in some minor flaws in the images (eg: chromatic abberation), but hell, even the expensive lenses end up with some of these flaws, like CA.
A Pentax + kit lens would be fantastic.
A Pentax + the Sigma or Tamron lens you were looking at will also take great photos. Once you get into it, then decide on what lenses to invest in.
Don't get
Phoenix or
Quantaray. I've never even heard of Phoenix, but Quantaray is garbage.