im thinking about replacing my desktop with a laptop. I have a sweet 2.1 speaker system, im sure I can connect these to my laptop at home. how good is the on board audio on most laptops?

also, I know there are different chipsets, but how good(or bad) are the mobile graphic chips? I have a geforce 4 ti4200 with 64MB of ddr ram on my desktop, would I have to spend and arm and a leg to get something even close to this level of 3d on a laptop? I see that the high end video chips are on the high end laptops which i cant afford, im looking at mobile radeon 7500 with 32 mb ram, what does that perform like?