Considering get an A5

What A5 are you wanting to get? The mods will probably be very similar to what you can do to an A3.

RS grilles, facelifted components, aftermarket splitters/diffusers. Usual suspects.

2.0 tdi or 3.0 tdi ?

3.0 is the one .

Coupe or SB? Went from A3 SB to A5 SB never been happier.

Coupe looks better but for everyday useage I would go for the SB, gets tiresome with 2 doors in the end when you want to bring passengers.

Quattro with 2.0 TDI is a safe bet as well, stage 1 tune will get you around 200bhp. Heard 3.0tdi can have some problems with the intake, Overall a more expensive Engine to deal with but ofc more fun to drive.

Aftermarket mods are plenty, like the A3: Honeycomb grille, mirrors, diffuser and spoiler. The A5 looks so good stock so not much thats need to be done other then tint, new Wheels and lower it in my opinion! If you get TDI pick up the black chrome or chrome end pipes for the exhaust tips for 50p as they look so much better then the standard TDI Non s-line pipes.

You should definitely try and get S-line exterior with alcantara seats and B&O sound system, audi Concert is ok and works if you cant find one though.

you wont be disappointed with the switch though coming from A3!

I went from A3 to A5 coupe, love it. Haven't needed to do any mods as it came with everything I wanted apart from reversing camera which is just too expensive.