I reckon 2x 3in is overkill TBH marco, 2.5in would do just fine.

Reason I was asking is im thinking of sticking to twins on the Chaser and exhaust wise im thinking a twin system all the way.

Aside from probable performance gains, most my reasoning for it is ive done a lot of research etc, and the longer and smaller bore (without being restrictive) the pipe is, the sweeter it seems to sound.

If possible, id prefer to have the silencers as far from the tailpipe as poss, as dont know exactly why, but seems to make it sound better, not volume, but actual tone. I mean like whatever silencers you need to get down to the DB level you want as close to engine as poss, then just plain pipe from then on.