Pioneer are well known for their quality h/u and speakers. Ive always had Pioneer headunits and I havent been disappointed yet!!! Ive currently got the new(ish) 8400 which is awesome!
With regards matching evrything up theres no need. I use to believe that sticking with the same brand throughout would result in better sound quality, but its not true. Although Pioneer speakers are good (in particular the Emotions), I would, personally, recommend a set of Infinitys. I have Infinity 6x9s in the back and 5.25" coaxals up front. The sound quality is superb. Also, if you can, make sure you buy some three way speakers and not two way as, again, the sound quality will be slightly better.