In what way do the current components let down the Superlight’s ride? Just feel sluggish? Chances are everything is heavy on the build so it’d be minimal gain I reckon. Secondhand is the way to go if you want to start dropping weight. £150 should get some decent lighter forks (Sids, Fox, Durins, etc) and around £70-80 will get whatever lighter wheel you fancy. Stem is a 70-80g saving at the very most.
The way the forks are set up will also make the front end feel particularly nimble or sluggish. Personally, I enjoyed my Superlight most with 100mm forks as it kept everything sharp and snappy. Experimenting with sag, rebound and any compression controls you might have change the feel of a fork quite a lot. I would be looking at tyres and fork set up before anything else with regards to how the Superlight rides.
I have some Fox FIT 100 RLC’s and a Pro II hub built with Stans Alpine rims if you decide to look in to new components. Wouldn’t be after much as I just need them out of the house.