What's your budget for a 'budget' projector? And what dimensions you'd consider travel size? Weight limitations?
I agree with lespurgeon, you're probably better off buying speakers and hooking them up to the projector. But if you are keen on buying a projector with built in speakers. I know the BenQ W1100 has some pretty good onboard speakers. They are 10Wx2 (about 20W total) and they'd give a good kick if that's what you're looking for. However I wouldn't consider the W1100 a budget projector (budget = usually under $600 i would assume). If you're in the entry level range and would be willing to spend in the 1k range, then this may be something you're interested in. The W1100 will definitely deliver great imagery that far surpasses its' audio capabilities. Sharp images paired with superb picture quality. The W1100 is also a bright entry level 1080p projector which is capable of throwing extremely large images. You could go up to 150" diagonal throw easily.
What will this projector be mainly for? For HT or for presentations?