I agree with Ziggy, Gmax is not the way to go.
What are you looking for from your suspension - looks, handling, both? I know it's only a 316 but if you have good handling you can still give some of these FWD codgers a damn good run for their money
If you want both but don't want the hassle / flexibility of adjustables then go for a fixed rate, uprated kit - H&R (as Ziggy said), Spax VSX (I personally use the Spax PSX adj kit, it's excellent), Eibach, F&K... there's loads of good options for around Ԛ£200-250 for the kit (4 shocks & springs).
If you want only looks then you can just buy a spring kit (same companies do 'em) and put decent standard shocks on e.g. Boge (from Euro or GSF). Cheaper, will look fine, but this will never work as good as a matched kit.
As for exhausts, if you only change the back box then you won't really get any performance benefit, it will look better and give better sound but the performance benefits are gained primarily before the exhaust gases even reach the back box (mainly in the manifold). Again, if it's looks you're after then just choose whatever looks good - even go to one of these places that make the bespoke exhausts (e.g. "Eurosport", I think they're called). They'll tune the looks and sound to what you want.
If you want peformance you need to look at a full system, but that's much more expensive - if you really want performance you'd be just as well looking at dropping an M42 engine in your car (without telling the ins
)
Best of luck with whichever you choose!
'89 325i - was an SE but not anymore, was bronze-beige metallic (yeuch!) but now techno-violet (thankfully)
'89 Toyota Corolla GTi-16 - track, hillclimb & sprint car (yeeha!)
'08 Buell XB12Ss - American engineering at it's 'best'... good fun though
