I actually made some measurements of the voltage driving a MG 1.6 when playing at an admittedly very loud level with demanding music. I concluded that my 600 watt/4 ohm amplifiers are not really overkill. They approached clipping. However, most of the time, and with a more reasonable volume level, 350 watts ought to be sufficient. I am now using CI D200 amps that are good for 350 watts at 4 ohms, and the 600 watt amps are busy driving subwoofers.
Your little tube amp will certainly drive the Maggies, and it will sound good, but you will not realize the real potential of the Maggies until you get a much more powerful amplifier.