Sounds (and looks) good to me. Given the fact that nobody has managed to crack the ECU on the 8.5 yet, I'm tempted to have a test drive when they come out.
We have to face facts that following the Brexit vote the pound devalued by about 7.5% and if the B9 is about 2.5% more expensive than the B8 then buyers should expect to pay 10% more for a 2017 S4/S5 than in 2015/16. No point in waiting either as I can't see how we can avoid a 'tariff war' with the EU so German cars are just going to get more and more expensive for UK buyers.The S4 configurator and pricing is finally up on the German Audi website. It's going to be very easy to rack up a huge bill with all the options! Hopefully the UK price won't just be the EUR to GBP conversion...
Don't forget that the B9 is likely to have a 'new' ECU too so it might be a while before it is cracked. Now I'm sure that the B9 S4 will be a great car but the extra performance over the B8 S4 won't be astonishing, and certainly not the level you are looking for on a B8 stage 1.
Also one more point to consider is that the EA838 is a new engine. The stage 1 and 2 mods on the EA837 have been proven to be reliable. Mods on the ES838 have to be considered a risk. That's why I'm happy to get a stage 2 on my S5 now that it is over 1 year old (although I don't have the ****ing choice do I?), whereas if I bought a B9 S4 I'd be inclined to wait until the warranty expired before having any engine mods done.
It wasn't so long ago that I asked Arin from APR about the ECU on the B9 (it is a Bosch MG1) and he indicated that it was going to be a big effort to crack it. APR have a thread going on Audizine about their planned new stage 3 for the B8 - take a look at the comments. APR have a habit of tempting the market and then taking a long time to deliver.Over at one of the US forums, there's report from APR that they have cracked the B9 ECU and a stage 1 tune isn't far away.
On the German configurator the S4 has the upgraded larger instrument cluster. Be a nice touch if that's included in the ukI have a PDF of the April 2015 A4/S4 pricelist and the S4 Saloon Nav was £40,085 and the BE £41,160. I suspect that what you found there were not prices for the B9 but for that same B8.
The B9 S5 coupe is now listed on Audi's German website. I did a rough calculation and it appears that there is a 2.5% price increase over the B8. Also there did not seem to be any extra options included in that, e.g. virtual cockpit and LED matrix headlights are priced optional extras.