Spring clips suck real bad, so you certainly won't be hurting value. But then it probably won't help much either. The typical "audiophile" mods (caps, resistors, wire, clocks etc) are where you can start throwing buckets of money right out the window -- even (or maybe especially) if performed by a modding company.
Effect on Value if I Update Speakers?
I recently acquired a pair of KEF 101 speakers. I love the sound, but alas, like many vintage speakers instead of binding posts they have tiny spring-clip connectors. This, of course, makes the use of heavy gauge wire or wire terminated with spades or plugs impossible. I'm considering updating these speakers by replacing the spring clip connectors with high quality binding posts, as well as replacing the thin internal wire with something more substantial, and recapping. Assuming I do an expert job, what would be the effect on the value of these speakers were I to do this updating?