I would take the Sigma 50mm 1.4 over the Pentax 50mm 1.4 any day. I'm a huge fan of Sigma lenses, and have been impressed with the ones I own.
The way I see it, the Pentax 50mm has the advantage of being small. But the Sigma has better image quality, especially wide open, has silent HSM autofocus, and it comes with a lens hood, which the Pentax lacks. I also think the Sigma looks way cooler on the camera, whereas the Pentax looks like it is straight out of the 80's. And the fact that Sigma has a much better warranty doesn't hurt either (at least in US, 4-years vs 1-year).
The Sigma also has a much higher used resale value than the Pentax. The Pentax 50mm goes for about $230 used on eBay, whereas the Sigma will go for close to $400.
As far as the cameras, I would take the K-x over the K-r, mostly because I think the K-x looks cool, while the K-r looks slightly awkward to me. The K-x has a smoother, more windswept design, while the K-r is a bit more blocky and angular, and is pointy on top. I also love the chrome accent that runs around the top of the K-x. And I always use the center focal point anyway, so the lack of focus indicators in the K-x viewfinder means nothing to me. I also like how the K-x doesn't require an adapter to us AA batteries.
But if I were you, and they wouldn't give me cash to buy a new camera, I'd take the K-r, and then resell it before even opening the box, and use the money to purchase a K-30. I just sold my beloved white K-x to purchase a K-30. I sold it with the 18-55mm lens for $390 (netted $350 after fees/shipping), and ordered my white K-30 18-55mm kit from Singapore for $750 shipped.