The clunk is in the driver's side front? That could be a number of different issues. If you're not suspension
savvy, I'd have someone inspect your suspension components. Sway bars make a big difference in handling
and are considered by most as one of the more cost effective modifications.
Strut tower bars are another story. A front strut tower bar doesn't always make a lot of difference, but the
GD STi's benefit greatly from a rear strut bar,
but only in the X or V-brace designs. Rear strut bars alone
are almost useless without the brace. Cusco makes a V-brace, which I have in my trunk:
http://igotasti.com/vBforum/attachment.php?attachmentid=4297&d=1362448871
http://www.rallysportdirect.com/Cus...-Models-inc-1998-2001-2-5RS-2002-2007-WRX-STI
I have the Group N tranny mount installed and I feel that it made a noticeable difference.
As far as coilovers go, I'll leave that discussion up to the other guys here. I personally have not had
very good experiences with coilovers over the years, so I'm more of a struts/shocks and springs kind
of guy.
I guess I didn't realize your fender was already damaged. If you're going to replace it anyway, then it makes
a little more sense to choose whatever fenders you like. I just figured that, if you were replacing them just for
looks, the money could be better spent elsewhere. Get a hold of some local body shops and tell them what you are
thinking about doing. That way, you'll know who to trust in the event that you need painting or adjustment work
done. It's always better to plan this stuff out
before buying the parts.