STI Mav

Afternoon all, just looking for some assistance from those of you who have decatted your Hawkeye Impreza or maybe know of the situation, as I'm now in the process of trying to make my mind up on wether to do this or not.

Now my understanding of the 2.5 ltr exhaust system, is that there is a decat downpipe, matted to a decat section then the centre section and then finally the backbox. As per the image below,



Assuming this is correct it seems you can buy the 2 decat parts independantly of each other from the likes of ScoobyWorld. The other option is to buy an "all in one" decat section similar to one of the two below,

http://cgi.ebay.co.uk/SUBARU-IMPREZA-WRX-STI-3-INCH-DOWNPIPE-AND-DECAT-01-07_W0QQitemZ140357137214QQcmdZViewItemQQptZUK_Cars Parts_Vehicles_CarParts_SM?hash=item20adeff33e
http://cgi.ebay.co.uk/IMPREZA-2-5-WRX-EXHAUST-MILLTEK-DE-CAT-DOWNPIPE-3-PIPE_W0QQitemZ230447764036QQcmdZViewItemQQptZUK_Ca rsParts_Vehicles_CarParts_SM?hash=item35a7c1d244

What I need to know is, is there any value to doing the 2 parts seperatley, perhaps just the down pipe or is recommended to do both parts ??

If this the case, has anybody brought one of the "all in one" sections from the likes of Milltek and if so can anyone confirm wether it's a 3" pipe all the way through, as my centre section and backbox are only 2.5" ??

Also wandering if anyone has brought one of the cheaper ones and if so what's the quality and fitment of those like ?? Is it the usual Ebay crap that's best avoided or does it do the job and fit without any issues or problems ? Again if anyone does have one of these are they able to confirm if it's a 3" all the way through or does it narrow to 2.5" to mat onto a standard exhaust system ??

All assistance appreciated !!

Cheers

Mav