Just because you have old Pentax consumer grade zoom lenses isn't the best reason to decide to go with a new Pentax digital body. That 28-80 and 80-210 and 100-300 are mediocre consumer level lenses that you should not get excited about but are worth a little used - but not a lot. The current kit lenses sold with new pentax digital bodies are better lenses.

The good news is there are Pentax enthusiasts out there who like to shoot with older Pentax bodies, and some of the stuff you have is worth a bit to them.  That 1.7x AF adapter is going for about $350 used on eBay.  That's the best thing to do with it, because it's not something you're going to use. It's purpose is to allow someone to add newer lense to focus on older (screw drive focus) cameras. Take the money!

There are also people out there that might be interested in the 50mm for mirrorless cameras. I'm not sure if Pentax primes have a following, but have a look yourself.

- Go to eBay
- Search for the item
- Ignore what you see, and click "Sold Items" as a filter, then you see on average what things *really* sell for.

So you probably have between $500 and $600 worth of stuff there which is a decent starting budget for something more mainstream. Even if that something turns out to be a newer Pentax digital camera with current kit lenses.