As a man who has had a half dozen or so catback configs on his car let me help a little. If you are NOT super or turbo charged get 2.5 inch I have tried 3 it is a no go.
Here is the reality for an easy cat back you have 2 choices megan or OBX but you want 2.5 inch piping so you want megan. Now you get to decide do you want a regular muffler or a fart cannon. That is it no one really makes an exhaust for these cars. Personally I think the exhaust I created with a TRD muffler is one of the best sounding exhausts I have ever had / heard and the best part is how quiet it is while cruising. So yea sorry not really much to pick from any more. I made a tutorial on making a custom exhaust try using that.
JP 3 Inch Cat-Back (JP-1MZFEScb) Very expensive 3 inch nice quality
Greddy (
http://www.greddy.com)
Greddy Evo 2 Cat-Back 3.0L V6 (GRD-10116601) Discontinued Sounds good has that large fart cannon civic look hard to find.
Apexi (
http://www.apexi-usa.com/)
APEXi World Sport Cat-Back 3.0L V6 (104-KT02) Discontinued Sounds great nice look beyond hard to find
OBX Racing (
http://www.ebay.com)
For Camry and Solara V6 3.0L 3" pipe full catback. Nice look JPP clone great sound 3 inch piping means loss of low end on a regular V6 cheal 300 shipped
JIC-Magic (
http://www.jic-magic.com)
All Engines
DE Type 1 ST Catback (MCV20D1-ST)
DE Type 1 Sus Catback (MCV20D1-SU) I know very little about these I remember them being expensive.
Megan Racing (
http://www.meganracing.com)
All Engines 2.5 inch piping
OE performance style non fart cannon ( MR-CBS-TSO99V6OE) Dual tip great sound not too loud 2.5 inch pipe oval muffler decent price
Drift Spec Z N1 style muffler (MR-CBS-TSO99V6DS) Standard angle fart cannon think fast and furious and you too can life you life a 1/4 mile at a time. Sounds good works well decent price
Custom
Very easy to make can sound great check the links in my sig.