Don't know if your 02 is the same as my 07, if so it's 6x9 front (component) and 6.5" rears.
I put Polk components in the front and some Infinity Reference 6.5's" I had laying around in the rears and the improvement is significant, even with the stock HU. I'll get the Scion HU in and then it'll really be nice.
The Polks put out some impressive bass.