How much faster of a sub is the REL T5X vs SVS SB12-NSD

Looking for some advice as to how to determine how much faster one sub is from another. I’m not sure how to determine this just by reading the specs and could use some help in educating me with this.

Currently I have the SVS and sounds good but feel after all my adjustments and crawls, just can’t get the slap on some of the bass I desire. Everything I’ve seen about the T5X is it’s one of the fastest subs out there and blends well with Maggi’s 

Main speakers: Magnepan .7’s

Sub: SB-12NSD

Rogue RP-1 Preamp

Carver Crimson 275 Amp (Yea,I know about the test’s and read all the posts about it, it sounds good, so please don’t hijack this post with comments regarding the amp.)

I’m really tempted to take advantage of the REL Home Trial, but hope I can get some assistance first so can make an educated decision.

Thanks