Welcome Nee
Different tanks (toppers) use different kinds of coils (heating elements which vaporize the liquid) which have different resistances which in turn need different power levels to run properly. You don't mention what your original tank is or what the resistance of the coil is.
In "general", tanks with higher resistance coils (Aspire Nautilus for example) don't need to be run at super-high power because the coils would burn (which then burns the juice which then sucks!) When you use something like the Subtank Nano, it's coils are usually either 0.5 ohms or 1.2 ohms. You need more power applied to heat the coil enough to vaporize the juice.
So, my "short" answer is it might not be necessary to get a different tank. However, I don't know a whole lot about the Sigelei 100W mod. I can't tell what topper you're using, so I don't know if it's over-kill, under-kill, or just right....
When you can, take a read through these blog articles. There is a LOT of information on terminology, and battery safety.
(18) Baditude's Blogs | E-Cigarette Forum
Keep asking questions - folks here will be glad to help where they can....