Hi Japer
Delay options, EQ options, different slopes rate options are in a way, over kill for your project.
If you go to this site’s library, you will see that JBL recommends the JBL 5234 electronic crossover network equipped with a 52-5140 crossover cards for the 4343.
And someone should chime in here with a response chart on the 52-5140 crossover cards. But, it does appear that a 12 db/octave slope rate most closely matches the 52-5140 crossover cards.
Since, most electronic crossovers on the market today have 24 db/octave slopes, finding a new 12 db/octave slope unit maybe be difficult.
Please take a look at the Ashley XR1001 crossover.
While, the XR1001 does have a 24db/octave slope rate, which is higher then the recommended slope rate of 12db/octave.
It does have a "response" control that allows you to adjust the depth of the crossover point.
And this should allow you to get an overall response that very closely matches that of the JBL 52-5140 crossover cards.
Also, I do know from experience that Ashley crossovers have a very low noise floor.
So, they will run very quietly in a home stereo environment. And that’s my $0.02 on the subject.
Baron030