I would politely disagree in regard to Dinan. You can find better upgrades for less $$ from other manufacturers rather than Dinan.
UUC is a great place to check, as well as Ground Control, RD Sport, ACS, Hartge, Eisenmann, ECIS, Jim Conforti from the bigger names.
I would not buy Dinan intake for many reasons. It is not a perfect design at all with the filter sitting too close to the ground and collecting all the dirt and water. Dinan even offers a "sock" over the filter to protect it from the elements... talk about restricting airflow.
Check ECIS or Conforti instead.
<img src="http://www.imagestation.com/picture/sraid10/p024a747b87f9fb6ed916f19f12f92dc2/fe034090.jpg">
325's can benefit from a free-er flowing exhaust, but not much. Basically chose by sound, looks, built quality and price. Some of the best ones are: Eisenmann, RD Sport, Super Sprint, ACS, UUC, AA and, if you want loud, B&B Tri-Flow.
Just shop around and see for yourself what fits best.