Ramrod340: By "adding to the safe" do you mean "investing in for profit" or for buying and shooting and keeping around for a while?
The pistols you mention in 22 caliber are a bit hard to find these days - especially on the used market.
I have shot both Model 18's and Model 17's in caliber 22 L.R. in the past and they are dreamy.
I currently just own four of those (2 M-18 4 inchers and 2 M-17 8 3/8 inchers) they are all either mint condition or unfired new in the boxes.
They are (in my opinion) just to valuable to take out shooting these days.
I often wish I had kept a shooter quality pistol in either model.
I have been looking for a Model 617 in 6 shot configuration (preferably) and at a livable price for quite some time now.
If "I" understand things correctly the Model 18 S&W's were also called "22 Combat Masterpieces" - I could be wrong about this as well but I think the Model 17 S&W's were called K-22 Masterpieces
- anyway both the Model 17's and 18's are superb pistols.
And I am pretty sure the S&W Model 617 came in both 6 shot and 10 shot configurations at different times - 10 shot being the latter manufactured style
I think any of the 3 models you are considering would be a good investment if you are collecting or an excellent pistol to shoot if interested in that.
Good luck.
Hold into the wind
VarmintGuy