This is a smaller 2x12 cab with approx. 90 liter volume. Your TTC 2x12 British Vertical has approx 135 liter volume.
Dirk recommended a pair of Invaders. I'm currently thinking about putting a Reaper HP and an Invader into my cab. I saw that demo on youtube and I think both a great sounding speakers. What I would be interested in what would be a 'better' combination with regards to open or closed back and to more or less volume of the cab?
I'm using a Splawn Street Rod and a Marshall JCM 410h with an 2x12 JCM 800 1936 Lead with Celestion G12-65
First: In that big box with the convertible back ... you have lots of good choices ... but for maximum versatility, I'd go with my old fav the ET65 & Retro 30
Second: In the smaller box ... The two Invaders would be good, especially if it's closed-back ... if It's open go with one Invader & One ET65; the ReaperHP/Invader combo is very close to the same tone overall ... so that would also be a fine choice.