Hey Ash,
Depending on were abouts you are based. Most Audi delears offer a fixed maintenance price list for vehicles over a certain age.
That the price for front pads is £139 and for front discs and pads is £279.
Link reference
http://www.audi.co.uk/owners-area/servicing-maintenance-mot/fixed-price-services.html
Now this includes fitment as well as a 1 or 2 year warranty on any of the parts fitted.
That said initially I had a slight argument with the dealer as they said to me they cant do it for the fixed price and I said well its stated that you can as its what you advertise, so it turned out that if they did it they would be making a huge loss as it worked out to around £540 "for discs and pads" as the DTM has drilled 320 mm discs in front with special pads compared to the normal 2.0t that have 320mm but non drilled discs and ordinary ate pads.
Well I took it up with them and said that on the website it qualifies as the vehicle is up to a 2 litre. The only exception is RS and S models including the Audi S3 as well as any vehicle fitted with ceramic brakes.
But low and behold they did it for me and funny enough ever since that incident every other Audi dealer I have been to they have done it with out any question.
So if you want your stock option. I suggest going to Audi to get it done.
On the other hand if you want to go bigger and better you can upgrade to 345mm disc which come standard on the S4 in the B7 range thou they arent drilled but they do offer more braking area. As our vehicles technically have the S4 calipers. The only downside is you may need to shave the caliper on the top to get the disc to fit, because I believe the S4 has a different caliper carriers. That said you can easily buy new carriers and not have any issue or just buy a second hand pair. Its really up to you and your budget.
http://www.ecstuning.com/Audi-B7_A4-Quattro-2.0T/Braking/Performance/ES6241/
That is the discs and caliper braket I was referring to now I know you can order those caliper brackets on there own. I will try and source the link.
If memory serves me correct this one can be used
http://www.ecstuning.com/Volkswagen-Passat_B6-FWD-2.0T/Braking/Performance/Front/Stage_1/ES8542/