Originally posted by Bui ...I end up with lost of photos with burned highlight and very dark shadows...PP improved them somewhat, but I can't say they're super pretty...
Post some photos that are giving you trouble. We can offer exposure and processing suggestions.
Blown highlights are very difficult to fix with PP. What exposure mode are you using? Are you using exposure compensation to "underexpose"? Have you tried bracketing or HDR? In harsh light, consider zooming in more; a narrower scene will have less variance in lighting.
The K-1 will give you a small dynamic range benefit over your current KP, much less than the improvements you already got by going from KX to KP. In very rough terms, going from the KX to KP gave you 1.5 stops of dynamic range, going to the K-1 will only add 0.5 more. Most blown highlights will still be blown with the K-1. but that extra dynamic range gives slightly more leeway to lift shadows during PP.
In my experience the main benefits to the K-1 are less noise in dim light, thinner depth of field if you like that style of photo, and better image quality at ultrawide angles. The KP can already do pretty well in those niches so unless you do a lot of night photography, thin depth of field, or ultrawide I don't think you'll gain much from the K-1.
Downsides to the K-1 vs the KP are extra size, extra weight, and possible need to buy more expensive lenses.