Rax48 vs XB8-T on 2 Gigabit Internet

I am currently saving up to get a better router or possibly switch over to a mesh system. In the meantime, I currently have my old Rax48 and this new XB8-T modem/router combo from Xfinity. I've heard these Xfinity modem/router combos are trash so I bought a Surfboard S33v2. Now with my new upgraded modem I should be able to get my 2gig speeds however I am pretty sure that I am being bottlenecked by the Rax48 because I can't get a speed test (modem to router) higher than 914mb.

So my question is this. Should I just bite the bullet and use the XB8-T until I can afford the new router or is there any way to unlock more speed from the Rax48?