Your choices are good ones, but a good SSP or springer will fit the bill for plinking fun. For a cheap, all around great pistol, the Beeman P17 is a fantastic bargin. Great plinker and very accurate.
As far as future potential in regards to upgrades, any one of the Crosman pistols will suffice. Though a Crosman made gun, the EB22, it is rather limited in easy mods. Mods can be done, but require a great deal more than the simple removal of factory parts and adding custom like with the other guns.
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