JOHN DOE <>
A tailored recommendation can only be offered if we know what combo stone you have, what knives you're sharpening, and what you want out of your knives (i.e. what you're cutting). Might sound silly, but true...
1) Which King combo: 250/1000, 800/4000, 1000/6000, 1200/8000.?!
2) You have german knives (e.g., Wusthof, Henkel, etc.), or JapaneseKnives (if so, what knives/steel)?
3) Is this a utility edge for meats & veggies & everything in between?
Odds on you needing a polishing stone like a Snow White are highly unlikely. Possible, but unlikely.
Are you flattening your stones; do you need a flattener?
Do you damage (i.e., chip/bend) your knives; need a low grit stone? My premise is your combo stone, if its a 250 or 800, may be adequate for bevel setting & repairs. Therefore the Latte expense might not be necessary.
The Fanatic 3 pc set is gonna get you a 400, 2000, 8000... plus your two Kings, whatever they are.
If you just want a set, the Shapton Pro set @$177 http://www.chefknivestogo.com/shpro3pcset.html
is an option that will more than likely give you as refined an edge as you'll ever need. That will leave you with a 320, 1000, 5000... plus your Kings, whatever they are.
I LOVE the Green Brick, but I don't like grinding down a 400 scratch pattern with it. The GB creates a finish more refined then you might expect of a 2K; it produces a mirror polish. I understand you have your Kings to supplement in here, but it's all a matter of what you have, what you want to incorporate into your progression, and how versatile you want your new stones to be on their own.
I think the Shapton Pro set offers a more versatile set on their own, but again what are you doing with your knives & what knives are they?
If you just have soft steel, this entire conversation is moot.
The CKTG 5 pc set has an awesome set of stones in it (Beston, Bester, Rika) that can really do anything, but it seems like you just want stones.
You might want to piece together a set with your Kings in mind... whatever they are. A...
Bester 1K or 1200 @$49.... http://www.chefknivestogo.com/bester1200.html
Green Brick 2K @$50... http://www.chefknivestogo.com/naao2kgrbr.html
Suhiro Rika 5k @$50... http://www.chefknivestogo.com/suri50grst.html
w/a lapping plate w/holder @$50... http://www.chefknivestogo.com/xxcdiplandun.html $20 less for plate only.
...is the same cost as the Fanatic set that will give you a major improvement over your King combo - plus you get a diamond plate for lapping.
If you already have a stone holder, I would replace the Bester with a Nubutama Ume 1K @67... http://www.chefknivestogo.com/nubatamaume1k1.html
and the cost would still stay the same as the Fanatic set.
Latte 400 @$59... http://www.chefknivestogo.com/la400grst.html
Nubutama Bamboo 4K @$100... http://www.chefknivestogo.com/nuba40.html
...are stones I'd love to fit in your set, but again... I don't know what you have & what you're doing.