My big rig used to be an Aggie DB750 thru an Aggie 412. It did in fact play wonderfully with all my basses. I'd say it was voiced a tad darker and richer than most amps I've played, kind of in the same category as most Eden amps and many Ashdown amps I've owned or played. That said, I A/B'd it with an Ampeg SVT-VR and Bergantino 610 cab and ended up keeping the Ampeg/Berg setup, which seemed a bit tighter and focused with more punch. But all that's just personal preference.
The DB750 was an exceptionally well built amp (except for the handles on the front which were easy to bend). It was good and heavy and just as solid and reliable as you'd ever expect any gigging amp to be. However, If I were looking at buying something in the DB750 power range again I'd probably skip the Aggie and instead look for a Thunderfunk 750 or newer offering which has its roots in the Gibby (and I think Acoustic) amp design department - still the best match I've found for the Thunderbird along with Bergantino cabs.
A TB'er that has much more experience than anyone I know with nearly every amp/cab combo out there is Tom Bowles. I'm sure he could give you a very accurate rundown of whatever you're looking at.