Hi,
I am not going to be much help in your choice but I would agree going used. I have gone through a few amps with my Ariston and my current Exposure was £230 and sounds fantastic.
I have tried various others but you can get a top of the range amp from 10 years ago for a fraction of the price and it will really make your LP12 shine.
I don't know about your speakers as to what would be a good match but if you don't mind trading you can try two amps see which you prefer sell one and try another until you find which one is right for you and all the demo's are done in your room and at your leisure.
Sorry not much help. good luck and have fun.