Bro, i have that Sony system driving my Plasma 51"... All i can say is the sound is great!
I also got a chance to listen to that Pioneer at the mall, the sound is also fantastic! - it's a pioneer, so no question ask when it comes to driving music. But i think kahit alin sa dalawa, sony or pioneer, you will never go wrong because they are both into producing great products when it comes to music! Just my opinion... but your taste in sounds will choose which one is the best for you! - goodluck!