Two other pens you might want to look at/for are the Platinum Preppy (a very cheap clear plastic pen, intended to be disposable but which can be eye-droppered or used with a converter/cartridge) and the Pilot Metropolitan (a metal body with a cartridge or converter, about the same price as the Kaweco Sport; I found one once at a Walmart). Both tend to write very well.

My pocket-pen is a Pilot Petit 1, another disposable that can be refilled and dirt cheap.

Fountain pen ink does make a difference, but nib quality is probably the major factor.