That LA512 is definitely worth $150. I'm actually gonna be buying the white version of that washer as soon as all the ice and snow can bugger off.
Both the Speed Queen and extra large capacity Maytags are 3.2 cubic feet. The Whirlpool Cabrio has by far the largest capacity, but it is a steaming pile of garbage and not worth the plastic it's made of. The Whirlpool and KitchenAid direct drives are a larger capacity than the extra large capacity Maytags for sure, so if you need a large capacity, then that's what you should go with.
The Whirlpool has a very fast and aggressive agitation, but the base of the agitator is smaller than the KitchenAid. It is also quite loud. The KitchenAid has a slower and gentler agitation, but the base of it's agitator is larger. It is also much quieter than the Whirlpool.
These are all fantastic machines, except of course the worthless Cabrio. The Maytags are definitely the most reliable and dependable out of all of them. The Whirlpool would be the better direct drive choice if your clothes get heavily soiled. The KitchenAid would be better if you want a gentler wash and your clothes don't get very dirty. As for whether or not you should choose them over the Maytags? I couldn't tell you. The Maytags have the most gentle wash action while also being extremely effective at cleaning even the dirtiest of clothes. They also have a lint filter inside the agitator which is nice.
I am biased here because I love those old Pitman Maytags. My dream machine is actually a harvest gold center dial 806. Because of my bias, I'm not sure I can give you an objective recommendation. I have an extra large capacity Maytag from 1994, and that thing can easily handle my queen size quilt, but not a very thick twin size comforter mostly because the one I have get's full of air bubbles.
If I were you, I would keep what you have. If you need the larger capacity, then get the LA512. However, as I said before, that may just be my bias talking.