This is gonna require more than that if you are to do it without running into a wall of impossiblity .
http://en.wikipedia.org/wiki/Variable-frequency_driveYou basicly need a high frequency synchronous motor and a high current 3 phase drive if you want anything remotly efficient past the 400 hz AND controllable with a knob wich is a must , you also need alot of series batteries or an massive house dc supply . Single phase motors should be avoided because theres less torque for the same amount of energy. We are talking a minimum of 1000 watts and lots of money here with the most efficient technique . Use a single phase chopper pwm with a pulley and you will hit the torque maxima , go too fast and you might break the alternator , its basicly hell on earth . Just running this @ 400 hz with house current is an achievement on its own , nice Job Komtek .
Either that or you go linear amplification , but that too has its problems specially with those big parallel caps in the Stephen Meyers system , you basicly need a 0 feedback amp or some compensation with loads of current gain to get those transistor nice and full and keep that nice sine wave , add the bias to that and you see the efficieny dropping and snowball overheating issues come into play ... Quite complex .