You could spend less, perhaps use a smaller unit, however that 1800 watt size looks like a good 120/100v transformer winoguy17 picked. I like that it has a display of it’s load and built-in protection, two outlets, and an on/off switch.
Your amp’s ’power consumption’ spec is 400 watts max at full rated output. Your speaker’s efficiency effects that.
IF you use the amp’s accessory outlets to turn other equipment on or off, i.e. an FM tuner, TT, any device.. you need to add their load(s), that’s why I like the 1800 watt version.
Always buy with a return option, just in case it hums, or you don’t like it. I use one for my 100v TT, small load, smaller 120/100v transformer. Zero hum.
Just avoid buying ’too cheap junk’
If you do not plug anything else into your amp, this 1,000 watt one is enough, saves you a bit of money, also Amazon
I doubt I would plug two things into it, I just like left side/right side option which gives placement options.