I've taken my rear muffler off on my EA. The difference is noticeble in both noise and power.
The car is much louder esp. when the throttle is wide open, sounds awesome but the noise will prolly get you defected. However if you drive normally (i.e. not like a twot) no one will notice as the noise only becomes invasive at above 3000rpm. Ive also noticed alot more power available at top end. Prior to me taking the muffler off the last 750 - 1000rpm was a bit flat, the power dropped off enough to notice. However the last 1000 rpm is now fully usable as the power doesnt drop off without the muffler. I can go flat chat right the red line. Nice. All in all i say do it, its cheap and the benefits are awesome. Also be aware that when cruising the noise can be a little annoying in the cabin, but it is bearable, nothing the stereo cant drown out.
I bet $20 Shav will hit 2000 posts by years end...