"When I listen to other setups that tend to run for $1k+, I'm usually blown away by the clarity and definition of the sound that I hear."
A sub isn't going to help in the clarity and definition dept. I don't know how low your B&W's go so it may help in that aspect of your enjoyment.
I have several vintage pieces myself (including a 2270) and tried to find a vintage speaker to complete the system but to no avail. All the ones I tried were pretty fuzzy. A friend of mine combined a pair of Altec Valencia cabinets with a modern mid and tweeter combined with a vintage JBL alnico woofer. That's how I made it work for me.
A sub isn't going to help in the clarity and definition dept. I don't know how low your B&W's go so it may help in that aspect of your enjoyment.
I have several vintage pieces myself (including a 2270) and tried to find a vintage speaker to complete the system but to no avail. All the ones I tried were pretty fuzzy. A friend of mine combined a pair of Altec Valencia cabinets with a modern mid and tweeter combined with a vintage JBL alnico woofer. That's how I made it work for me.