I agree that GK's proprietary approach is a force that limited the potential success of powered bass cabs. My understanding is they were essentially powered extension speakers intended for use with GK combo amps...thus not fully compatible with regular preamps. These were moderately priced.
Bergantino had powered cabs based on their HT line. I believe these had line level inputs. They were expensive.
The only other powered bass cabs I can think of is the ISP Bass Vector series. The ISP Bass Vector Pro and Beta Bass preamp received very good reviews. From what I remember they were pretty expensive, and also the cabs were large and heavy (scaled for arena type gigs). As you probably know the market is now focused almost exclusively on small and light.
I think a big reason why powered cabs have not caught on is they simply were never common enough to break through. In order for a new product to gain a footing in the market, it needs high enough sales to break over from losses into profitability. If there is money to be made, more companies enter the market.
The GKs are not really designed as a powered cab and the Bergantino and ISP seemed positioned as high-value, low-sales-volume products. None of them ever made scale in the market, either as individual products or as a category of products.
Sweetwater has a Bass Vector 210 for about $800. Not sure if the Theta Bass and bigger Bass Vectors are still available.
Sweetwater has bunch of other powered ISP Vector cabs available, including subs, but they are intended for guitar, rather than bass. Also some are special order.
Ultimately I think few bassists are willing to consider the preamp/power amp path. Most would rather have an integrated pre/power solution. Most of the great bass preamps are rack-based. Racks tend to be big and heavy.
If you want powered cabs, it's not too hard to select PA cabs that will do a fine job. For best results you probably want a 2-cab solution with a sub and mid/high cab.