Although I can't do a comparison as I know nothing about the Sempron, I have a Celeron 1.5 M class laptop with 512 meg of ram and a 60 gig hard drive, and I love it. It's been amazing and can play every modern game/program I throw at it. Oh, it also comes with an onboard graphic chip with 64 meg of memory. I did invest in a creative sound card (Audigy) the plug in one on a card....what do they call it?...not becuase of the better sound but because it has ASIO drivers which speeds things up when working with audio files and loops when composing music. But most wouldn't need this as the inbuild sound is fabulous and compatible with Soundblaster. Mine cost $1,640 AUD about six months ago. It is an Optima Centoris - Australian brand - and has been amazing. Couldn't be happier.
www.optima.com.au