am not sure what you really want to build. a power amp IC to run the whole set up (stereo + Sub) or just a power amp IC to power your 30w sub-wooofer. as recommended by faidul, i would suggest you use the TDA2030AH. that way you have several options what to do with the device.
I have designed an audio amplifier of 40 Watt output. IC that i have used is LM4780, Specifications of this IC is Output power =60W THD =0.03% slew rate =19V/us CMRR =110db gain bandwidth product = 8 MHz The output power it can deliver is 60W which doesn't mean that it can deliver 60 Watt for any input, you will have to calculate the voltage you need to give at the input so that it gives an output power of 30W. i think the formula is given in the data sheet, Download it & read it carefully! All the best!
Id look at some of the newest output ics class d operation as well So that you can abreast of times Most amplifiers now and in the future will be class d operation some of which I note are now I2C controlled which you will also need to consider micro theory within this as well now Also pay carefull attention to packages many of which are now surface mount where the intergral part of the heatsink is incorperated into the PCB so dont rush into the first device you see Do some severe research before you dive into building an amplifier of this nature
TDA8947J by phillips now Nexus offers btw 25 4 channel 2channel Btl 50 watts incorperates soft clipping Standby and mute Output sc protection
or there is the TDA 7296 60watt Dmos amplifier class ab offered by sgs thompson
or look at the Tas 5709 which handles digital inputstreams i2C controlled Texas instruments
Always consider where technology is moving too example fibre optic couplings meaning mpeg audio down optical leads so you know that means Digital front ends Mpeg decoders encoders multiplexed channels inclusive bus commands for peripheral control
Dont forget also bluetooth which will mean mpeg streams So you need to be seriously investigating opto electronics as the way forward in conjunction with dsp pic and how you will deal with the current industrial demands Meaning that you will have to learn how to read write and push streams of all manor of contents inclusive typical bus architecture which runs along side this
and on a final.note there is the TFA9842AJ With intergral pwm volume control Phillips semiconductors small applications
So its not too long before we see the close of analogue systems and we move to pure digital not that class ab will be done away with but if you consider heat, efficiency and size plus intergrated controll It becomes obvious as does the network intergration side of this
