I've spent some time on these over the last few weeks. I tried the cheaper options first, then ended up going down the dearer route in the end 9H&R) as wheel wobble is an issue if you have original equipment wheels with the beveled inside edges. If you have, then regardless of spacer size, its essential from my experience, that you get spacers with a raised tapered beze in the middle to correctly seat the OE wheels - without these wobble is common, as the wheel does not seat correctly, so flat spacers are a definate no no.
In terms of the look youre after its very much personal preference and depends on what of- set your current wheels are.
As a guide B8 OE wheels are usually et43 and for me, with this offset, a 5mm spacer on the front, 10mm on th rear is ideal.
I did have 10mm front and 15mm rear, but whilst this looked ok on my winter tyres, when I swapped to summer tyres (same 255/35 19 size) the larger rim protectors stuck out a little too far for my liking and it looked like I had spacers.... or the wheels from another car, just not subtle enough for me. Again the spacer size you'll want will also depend on the brand of tyres you're running.
With regard to the wobble issues, its ussually the 5mm spacers that are problematic as they are usually flat, to machine from a billet and include the raised bevel is difficult on 5mm - Black Forest Industries (USA) is the only company that I've found that have the correct style in the 5mm spacer.