No matter what you buy there is going to be cost. Looking at your lenses I'm a little surprised you aren't think about a K-P.
There are three types of FF cameras
Action cameras, fast frames per second rate, great tracking and AF, but low MP.
Combination cameras, the best of which is probably the Nikon D850, which attempts to be everything for everyone and does a pretty good job.
Field cameras, landscape, pseudo macro, great images but lacking many of the features necessary in an action camera.
The K-1 fits into the last category. Not a great frame rate, to small a buffer for continuous action, but top quality IQ for the images you get.
Honestly, if you don't need the tracking capability a K-P will be a better choice than a D-750. It's an action camera.
A 6D compared to a K-1, don't waste your time thinking about it. A gain, because of the lenses you own, you'd be better off with a K-P.
Canon 5DmkII, again, unless you want the AF tracking capability, a K-P will be better.
At this price point you don't get everything.
You can have the IQ of the K-1, or the tracking ability of the Nikon or Canons, but at that price you don't get both.
Personally I always go for IQ. Circumstances can make up for lack of tracking AF. There are techniques to overcome the lack of it. Mind you those techniques get you a couple of shots when you might get 20 with a better tracking camera. But the 36 MP compared to 24 or less is always there.
You also might want to check the expense of the lenses you need just to get what you have.
From Pentax you will need at least the 24-70 and the 70-200 just to match your current capability. So you are talking
$1800 USD + 24-70 - $1000 + $1600.
You are looking at $4400 USD just to get pretty much the exact same capability you have now (except for the IQ for really big prints, and the slightly narrower depth of eld.) . To me, a K=P would be a much smarter solution. But hey, if you have the $5k I'm sure you can put together a decent package with any of those systems. And if sports or action is a big then drop Pentax altogether. Pentax in my mind has focussed on the basics of field photography.
Other companies focus on more sporty packages, but haven't done the things Pentax has done like in body shake reduction or Pixel Shift. And the only real compromise camera the D850, great IQ, acceptable AF and tracking, but low burst rate (FPS) it's twice the price and you still have the same lens expenses.
You didn't say how much you have to spend but. unless it's $5k USD or more, a K-P is your best upgrade. You have two quality APS-c lenses. You will get 22% more resolution on the lenses you own with a K-P or K-70 and it will be comparable IQ to the $5k system you are thinking about. For you it's a bargain, unless you want better action or sports. And every modern Pentax camera is abetter action sports camera than a K-5, K-1 included.
I look at the cost of a D750 with a 24-70 and 70-200 and ask "What are you thinking? Did you get a second mortgage?" Even the K-1 is the same. You are talking totally different league than what you have now. But hey, maybe that's the point. You want big step up, not an incremental step up. Unfortunately it's step up in price more than capability in every day use. It's the law of diminishing returns.
A K-P would be a big step up. You're talking about a huge step up. I wouldn't even consider a recommendation withuout understating what you want to better than what you have now. Especially since my wife is still quite happy with her k-5 and finds with lower quality lenses than what you have that it meets all her needs.
Her K-5 has 67,000 shutter actuation, she's tried both my K-3 and my K-1 and just says, "They are nice cameras but what I have is fine for me."
Looking at your ƒ2.8 zooms, I'd say K-P and DA 50 1.8 with what ever FA limited appeals to you. Increase your capability by building on what you have,
Last edited by normhead; 01-21-2018 at 09:51 AM.