I find the Can Tire 230AH 6s are great at a good price, although they have gone up $25 recently. They are East Penn Deka GC15s. I have four and no problems with running the MW etc with a 2000w inverter.
You do have problems with only two 6s, but not with four down to 50% SOC. If you ran the batts down lower than 50% then the inverter alarm would sound even with four 6s.
Can Tire has recently added a 215AH 6, which is at a very good price, looking at 230 vs 215, but I don't know if it is an East Penn. If it is, that would be the better deal with four of those.