I guess it depends what kind of tone you looking for... My favourite combo at the moment is a Genz Benz GBE 400 with the AE212. Great feel and sound, lots of volume, loads of EQ possibilities, and works really well for so many things. Other amps used:
GBE 1200 - good but not as good for some reason???
Markbass LMII - pretty good, not my thing
Markbass MoMark 500 - better than the LMII but still not quite there for me, a little coloured for my liking
Ampeg Portabass 800 - sounds good at low volumes, doesn't kick like I want with the AE212
Genz Benz STL 900 - so close, but can't quite get what I want EQ-wise on a gig; I like the Streamliner SO much better with a 110 or 115 cab
GK MB800 - has a great sound, but only one with the AE212; not as versatile as I'd like
Mesa Fathom M6 (early version of the Carbine) - very nice - similar to the GBE in many ways, I just don't like it quite as much
Aguilar DB750 - my second favourite, but doesn't seem to like all of my basses equally like the GBE 400 does
Thunderfunk 550B - it had possibilities but I couldn't seem to get a handle on the EQ; this one might have been my fault, but the GBE 400 is much easier for me to dial in...
Epifani 502 - no.
TC Classic 450 - similar to the Markbass, but has a little bit of digital "fizz" that I don't like
Bottom line... I have a few rigs at my disposal chosen for their use in particular situations, but the AE212/GBE400 always gets the nod for new or challenging situations.