Just get someone with a grinder/sander to fix the old Henckels for you Seriously...if it's an old one, they're great knives.
Pick up a CCK-1303. It's basic carbon and incredibly easy to sharpen/deburr, it's got a simple, near-flat profile that isn't overly complicated, and it's like $30.
You could find a flea market and go crazy!
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Remember: You're a unique individual...just like everybody else.
It really all depends on what you want to own in the future...if you like cleavers, go for the CCK, it's easy to sharpen, and needs to be sharpened often and can get pretty sharp, but it loses it's edge fast. However, it's easier to see the angle because the knife is so huge, easier to hold, and you don't get practice sharpening the tip like a normal gyuto.
I'd recommend to pick what kind of knife you want to sharpen mostly, and get the cheapest here:
If the cheapest is still pretty close to a good knife (and not orders of magnitude less)...then why not just get what you really want? You probably won't ruin the edge completely, and when you're done you can ship it off to someone to fix if it seems very far off.
One last piece of advice, when I started learning to sharpen, it was on straight razors. I picked up 5 wapi's or so (cheap but decent steel) and some were warped bad, some just a little...they took forever to do anything with and along the way I couldn't really tell if I was making it worse or better. But only once I got a real razor to sharpen did it go easy and the results were fast to test. So although you can learn a lot on a cheap blade, keep in mind quality blades usually require a lot less time on the coarse stones and sometimes a different approach. If you use a 4k+ stone on a good blade, it would take you a LONG time to really ruin the edge in a way that would cost lots of money to fix.
The CCK is a great cleaver. But if you are looking to practice sharpening I would get a gyuto to practice with more curve and a tip. Or even a suji just because it has a more similar profile. I would contact Jon from JKI unless someone has something to offer up. Also, what are you looking to spend?
thinning is part of sharpening.... maybe even more important performance-wise.
Get something that allows you in the near future to work on the edge, on the grind, and on the back-bevels.