Worked my way through a whole bunch of bassline synths like a hundred different TB303 emulators and several bassguitar synths like Raspier and such. I settled for two instruments that are a nice addition and each bring something different to the arsenal; EVM Bassline is a nice wavesample-based synth with a few charasteristic bass-sounds... and Odo's B-station 2 with is a bit more then your mediocre TB303 emulation.
Both added to the list in the OP, with download links