I know you mentioned the Sansamp was a bit "grindy", but have you tried the VTBass? I use that currently for my IEMs and that gives me a nice fat warm sound.
There is also the Two Notes Revolt Bass which I absolutely love the look and sound of.
And as Boodang said, the SpectraDrive is great (assuming it has essentially the same circuitry as the old RH amp heads, or at least can sound like them).