I hope you did the math to verify if the new drivers were a suitable match for your existing box. Be careful with a screwdriver in an electric drill. It's far too easy for it to slip and go through the cone. (Ask me how I know!)
I've always preferred to use external effects. That way if you find a combination that works for you then you can easily transfer to possibly a more powerful amplifier should need arise or if you enter an open stage.
May I humbly wish you good fortune with the build? If you do the science properly you should arrive at a good result.
It's a great feeling using the system on stage for the first time and it making you smile!
Steve, I know there's a time difference between New York and the UK but ten years is a little much don't you think?
Don't you have snow to shovel? We sure do here in Toronto!!!
Aside from that, welcome to Bass Chat!
The physical rotation of the volume control has no relevance to the actual output power the amp is producing. "Half volume" does not mean 100W being put out.
During my career I have used many speaker cabinets loaded with 18" drivers. I couldn't get on with any of them. Your experience may differ. As BFM states it's not the size of of the cone that matters. Look at Phil Jones Bass who use a bunch of small drivers to get really deep bass.
What a trip down memory lane!! I when I bought my first bass I plugged it into my Dad's hiFi system. A Leak TL12 pushed by the VarislopeIII preamp. I used the tape input on the facia and through his Wharfdale SFB3 speaker system it worked very well.
Looking back over the last 60 odd years as a bass player with an engineering education I muse at the time I spent getting distortion out of my signal chain. Now folks are deliberately adding it. Who knew? LOL