Well, I must say that schematic barely resembles anything suitable for a 450W amp. It looks more like something you'd find in a tiny cheap radio or a Gameboy or something. I don't think that design would work so well for a power amp, but you should take it from the more experienced people here than me. I see it's class A too, you're going to be dissapating a LOT of heat if you do it that way. Plan on cooling it with a pair of truck radiators?
I've never heard of a 450W amp with that much bias current. Also, why don't you use differential input stage? I see you have no global NFB either. You also need a way higher supply voltage, you need plenty of headroom, it's not based just on ohm's law alone. You need a lot more than ohm's law and transistor theory to design a 450W amp. There are so many things that modern amps incorporate into their designs that your circuit lacks.
To get a good foothold in audio design, you should check out web sites like
http://sound.westhost.com, he has a page there on audio amp basics, and read some books on amplifier design, like Randy Slone's "High Power Audio Amplifier Construction Manual" and Doug Self's "Audio Power Amplifier Design Handbook". I remember when I was where you are, it wasn't so long ago. You just need to read up a little more.
Good Luck!
P.S. I'm building some 450W amps too, but they're for 2 ohm operation. I have quite an extensive thread on it ("1kW MOSFET amplifier") you should check it out. My reputation here still suffers from this project, (it was worse before I decided to make 14x450W amps and 8x112W amps instead of 8x900W into 12 ohm amps) so watch out if you dive into something big too early, people will critisize you mercilessly if you don't follow their every bit of advice.
P.P.S. It's great to have more young people like myself here. I'm 16. Even though I think it scares some of the elders.
