Hi David
Did you try changing the bass with the DSP or just stay stock?? I agree you really need to get the bass right as it is the foundation.
As far as DIY been doing that for about 20 years now. I always wanted a pair of JBL large format monitors. Back in 2004 when I built the 4344 JBL still supported the heritage drivers so you could buy driver cores for chump change and get them re-coned and have essentially brand new drivers.
We also had a guy at Lansing Heritage who worked out equivalent crossovers without the tapped transformer attenuators that were no longer available. With that done you could build the crossovers and use any parts you wanted including "upgraded" the parts if you wished.
We also took out the noisy bi-amp switch which was an issue in the stock systems. So all in all if you could build a box and wire a crossover you could end up with a brand new speaker system for a 1/3 of the price of a vintage stock pair. Buying vintage you really have no idea what condition the drivers were in so half the time you would re-cone/re-diaphragm them anyway. So overall an attractive alternative.
Unfortunately those days are gone with the cone kits no longer supported.
I also own stock systems but really enjoy doing DIY. It's fun!
Rob