Nimitz

@Nimitz
Sorry for slow response, lots of hectic here currently.
Battery replacement is still in limbo but I've finally managed to get a return/refund organised for the blasted gels. Just waiting to complete that.
Esener is currently front-runner because price and also local company. They offer a very good price if you're willing to take 3 units, otherwise you need to go through a reseller.
Only caveat: the Esener battery doesn't seem to have a way to talk to inverters (via CAN/RS435/whatever), but I bought a Victron SmartShunt recently, so I don't really care about that.
The battery will deal with max. discharge protection itself and the SmartShunt can tell me where the battery state is at, and also remotely.
I have an RCT 2kW (genuine Voltronic), and aside from it's inability to deal with lead gel batteries, it's a nice little unit. I imagine the 3kW variant will do equally well.
FYI: both your inverter options seem to be Voltronic units, but be aware that Voltronic clones also exist.
@Coulomb did an EXCELLENT write-up about how to tell real from clone - do a forum search, you find it.
So to recap: I've pretty much decided on Esener, but don't have any experience yet, so will only be able to report back in a few months.