Thought it would be helpful if sports exhaust owners could update this wiki to help those trying to choose one from the myriad of options available. I've populated the table with a few systems I can think of, please add any I've missed and new lines for the same systems across different models:

Manufacturer	Exhaust Desc	Porsche Model	Cost	Desc of sound	Static Volume(dB) 0.5m @ 45 degs @ 3/4 max rpm	Sound file/video	Contributor
Roock
Dansk	S/Steel Cat bypass and 1 in 2 out rear box	3.2 Carrera	£500.00ish	A deffinate grumbly burble on idle and screams like a banshee at full RPM, lots of pops and bangs on the over run.	loud	to follow	Paulbav
Dansk	S/Steel Dansk 100 Cell Sport Cat and RSR rear boxes	993Turbo X50 430bhp	£2,000.00ish	Deep burble on cold start. Barks when pulling off or when revving low (similar to the old aircooled sound). Deep exotic sound on idle with a loud roar at full boost and high rpms	loud yet perfect and not intruisive for long highway 3,000 rpm cruising	to follow	911Thrasher
Oettle	Muffler bypass pipe welded across box inlet and outlet. Standard CATs	996 C2	£235 from Oettle to modify your own mufflers or £430 outright purchase from Sommerfield Tuning Germany	Low rumble at idle, Loud GROWL on rising throttle, Unobtrusive when cruising	106 bB	http://oettle.org/mediapool/50/504167/videos/PORSCHE_996_OETTLE_AUSPUFF.wmv	Pugley
RSR	The original mufflers are modified internally and externally resulting in a louder and deeper sound with no reasonance	996	400 Euro + 250 Euro deposit			http://www.carnewal-europe.com/cpx/p96195_after.wav	dan1502
Fabspeed
Evoms
PSE	Switchable	996 C4S	Originally: £1900 discounted from £2300 but recently increased to £3k to £4k (depending on who fits it)	Burbles at idle, howls through rev range, super bark at full bore	99dB off 106dB on	http://www.youtube.com/watch?v=pWwt0vmRCk0&fea...	Callughan
Supersprint
DesignTek	Sports (as opposed to Super Sound)	996 C4S	£595+2.5hrs labour+£30 of nuts/bolts+VAT	Throatier/deeper at lower/medium revs, loud on an open throttle, comes alive at 3.7k rpm	95	to follow	Mario149
SCE
Remus
AWE	Extractors/200-Cell Cats/Silencers. Adds about 30BHP	997S (Systems also available for other Porsche models)	£3000+	997S - Bassier idle. Quiet at part throttle. Hard-edged howl at full throttle. GT3 - OMFG! Check-out the sound clip...		www.awe-tuning.com/ UK Importer www.regal-auto.co.uk/	Ian_UK1
Borla
AfterHours
Milltek Sport	Cat back, cup system (British made!)	C2/C4 1998 to 2005	~£800, check discounts	Slightly deeper at idle, guttural bark at rev and overrun.	(approx.82db idle)		fot0
Europipe	996 Turbo Stage 1	996 Turbo	Not exactly sure at it wasn't broken down on the bill which included other things	Nice burble especially on overun. Loud when WOT. Fine on the motorway	@Goodwood 105dB @Brands 102dB	http://www.europipe.be/videos/Europipe_996_Turbo_stage1.htm	_gez_
Tubi	Tubi Style 997 Turbo Exhaust - 200cell cats	997TT	Retails for around £3000	Deep burble on cold start. Barks when pulling off or parking when revving low (similar to the old aircooled sound). Deep exotic sound on idle with a loud roar at full boost and high rpms.		http://www.youtube.com/watch?v=NRrqU-_Ab44	S3Nick
Cargraphic	ETS super sound	996 GT3	£900-£1250+fitting	very loud, burbles & pops on tick over, builds to a throatier sound in the mid range and screams like a banshee in the higher rev band....Totally transforms the experience, throttle feels more responsive and free flowing	103dB (A) 50cm away from tailpipeexit - at an angle of 45°	to follow	Red 3
B&B
Agency Power	Sports	997S	£520.00 plus 3hrs fitting	deeper burble lower down then barks further up the rev range		http://www.vividracing.com/catalog/exhaust-parts-mufflers-c-4246_5078.html	daggerpie
Manthey	sport	996 C2	£1570 fitted	Subtle at low revs-louder than stock, 'burble' on increase, bordering cup-ish at WOT	98.9	to follow	s_mcneil
TechArt
FVD/Brombacher	Export sound version (200cell)	997TT	£3000rrp	Cold start is angry, a deep exotic sound. Agressive when it needs to be @ WOT. Lots of turbo whistle. Sounds amazing and by far the best system I have heard for the 997tt (I ditched my Tubi for this system) They even do a titanium version which I am considering as it will shave off a load of weight.	I will find out	http://www.youtube.com/watch?v=aIpY7yWo-Ns	S3Nick
Kreissieg
QuickSilver	New 2010 Titanium Sports exhaust, using OE tips	997 Turbo	£3680	Incredible sound, very burbly on tickover and much more aggressive sounding up the revs. Half the weight of the OE		http://www.porscheexhausts.com/story/Porsche-911-997-Turbo-TITANIUM-Sports-Exhaust/289.htm	rpm1200
Capristo