Well heres the thing:
Most of us sampires/dexxers have a lot of stamina and to make any 2.5s weapon swing at 1.25s with 150 stamina you need 0 SSI. However, once you drop below 150 (as in 149) your swing speed gets bumped up to 1.5s.
Other examples (2.5s wep):
5 SSI at 120 stamina to swing at 1.25s
20 SSI at 90 stamina to swing at 1.25s
---Just remember that dipping below the stamina I listed will bump you up to 1.5s so it's still best to have a good amount of stamina.---
So it's up to you to pick what you like. But if you're going to be imbuing a soulseeker, yes, you should definitely lower SSI and bump others imo. You could do something like 5 SSI/150+ stam and change whatever. (I've never actually tried imbuing a soulseeker so I can't comment on that yet)
Then on other radiant scimitars (not soulseeker) if you have a turquoise ring with 5 SSI and a good bit of stamina, you could use that 5 SSI on the ring and completely remove SSI from your 2.5s weapon allowing you to have something extra, be it HLA, HLD, HLL, whatever. There's also things like Daimyo's Helm.
Lots of possibilities we can play with now so have some fun.
Hope everyone can understand this lol.