Cat Back, Stainless, 2.5" Diameter Pipe, Best Price as of 1/2007 ECS Tuning = $900.00
One of the louder exhausts, like Borla
APR sound clip:
http://www.youtube.com/watch?v=0Hd1T2ykAYo

Cat Back, Stainless, 70mm Diameter pipe, Best Price as of 1/2007 Vivid Racing = $1300.00

Cat back, T304 Stainless Steel, 70mm Diameter Pipe, Best price as of 1/2007 - Vivid Racing = $700.00, also at SFX Performance = $734.00

Cat Back Res and Non Res, T304 Stainless Steel, 2.75" Diameter Pipe, 100mm tips, Best price as of 1/2007 Stratmosphere = $950.00 Non res, $1000.00 Resonanted
Milltek Install - BlueTTop
http://public.fotki.com/BlueTTop/mods/exhaust/

Made in Sweden, Stainless, 2.75" diameter Pipe, used to be available on ebay for $695.00
Only one who has this that I know of is Seneb on AW
Website Link
http://www.jetex.co.uk/website/jetex_exhausts_chooser.php
Video/Sound Link
http://www.youtube.com/watch?v=EdWV4Rf_ImY
North America Web Site
http://www.hstar.net/jetex/index.html

Cat Back, T304/321 Stainless Steel, 2.5" Diameter Pipe, Best price as of 1/2007 APT Tuning = $935.00

You be the judge!
Steve's Custom Link, exhaust originally made for Sheep
http://public.fotki.com/ttschwing/exhaust_installs/custom-magnaflow-by/
Steve's Custom Video
http://www.modshack.info/images/mufflex.mpg

Possibly needed for aftermarket install-Thanks to MarTT
Center bracket: 8N0 253 461 C
http://www.worldimpex.com/parts/genuine-part-bracket_79578.html
Rubber hanger 1J0 253 147 C
http://www.worldimpex.com/parts/genuine-part-exhaust-hanger_79430.html

Cat Back Exhaust, T304 Stainless Steel, best price as of 1/2007 - TTStuff = $780.00 or Auto Parts Warehouse = $741.00 w/free shipping
Borla Install - Thanks Warren/stilljester
http://mysite.verizon.net/vze7srd4/Borla.pdf
Borla Sound link
http://www.straightfocus.com/tt/Borla_Exhaust-TT-1.mov

Comments - Good performance, high drone sound, one of the louder exhausts

Cat Back, Stainless Steel, 100mm tips, - The TT Shop aprox $700.00
Got mine from the Blue Flame Ebay site listed on MarTT's Fotki. $625/Shipped!!
Blue Flame/Forge Install - MarTT
http://public.fotki.com/martt/audi_tt/mods/blueflame/
Another Install - TTinWV
http://www.blackwood-wv.net/TTinWV/mods.htm#Blueflame%20Cat-Back%20Exhaust%20-%2010%20June%202006
Sound Links
http://www.thettshop.com/blueflame2.mov
http://www.thettshop.com/blueflame1.mov

Comments - Good Performance, more mellow sound
, louder than stock, but less than Borla and APR

Comes with several tip designs, T304 Stainless
http://www.supersprintna.com
Current aprox cost as of 1/2007 for all parts = $1300.00

Axeyrcat quote "Very quiet at idle and cruising speeds with pleasant bark at WOT. Very smooth sound -- not raspy at all.
I'd highly recommend it if you want to keep stock noise levels but replace them with superior noise that's a bit louder at WOT."