B&W bass, where next?

[Bowie]

Hi, I hope this isn't incomprehensible and that you can help, I have four B&W LF00507 bass unit speakers from the custom series CT8LR and would like to build a really nice stereo sound that can also be the L&R of a theatre system. The power amp is a Carver Sunfire TGA 5400, it gives 400 Watts per channel into 8Ω or 800 Watts per channel into 4 Ω. I still have the B&W CT8XO 2 active crossovers that are needed for the whole units but nothing else is left from those two original CT8LR speaker cases (please don't ask what happened, horrible). I am looking for some compatible mid range and tweeters to give a real presence and detail, and to do justice to the quality of the amp and bass units. Do you recommend internal cross overs after the terminal tray, or external multi channel active cross overs? I don't need it to be the level of the rest of the CT8's, just capable and accurate reproduction. Thanks for your time.