To me, the Markbass LM II has impressed me the most bang for buck. Haven't tried the LM III, but should be a touch better in some regards. I replaced a GK 1001 with an LM II. I A/B'd the LH1000 and LMII though AE210 and HX410 cabs. In these experiences and others, with some quite extensive shootouts I have been very impressed with the LMII, and have bought a second one as well. Is it the baddest on the market? No. Does it have the broadest feature set of all? No. Is it one heck of an amp for the buck that sounds really great and gets quite loud and very dependable? Absolutely so!!
The LM II or LM III will push a decent 4 ohm 4x10 quite well if the cab is at all efficient.
I use Bergantino cabs. Who knows what tomorrow brings with my rig of choice, but the Markbass heads are for real IME/IMHO. Especially for the money.
Listen to everything you can with as few variables as possible. Use same bass, same strings, same cab, etc....and listen to projected sound, not just what you hear right in front of a given cab. This is important with respect to most any gear, especially amp and cabs..

Good luck!!