It depends on your driving. If the majority of your driving is done at city speeds, then yes, the alloys will help a whole bunch.
You can always get screw-on Moon discs. They are secured by three small screws per wheel that slightly enter the tire bead. Needless to say, using them on a daily-driven car sounds scary. It would be a different story if, say, you put them on a track-day car, and the track was a salt flat or dry lake.
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