Forum member EricM had his Santiagos powder coated in smoked chrome colour. I think they look good, and having them powder coated does away with the potential problem of white worm corrosion that diamond cut alloys are prone to. Link to thread, including picture below;http://www.golfgtiforum.co.uk/index.php?topic=278775.0
I see that the Cades Apollo wheels are available in a number of different offsets and 2 different widths; 8.5" and 9.5". The spec for your Santiagos is 5x112 bolt pattern, 19" diameter and 7.5" width with an offset of ET51.
Assuming you'd be planning on getting the 19x8.5 version of the Apollos, the offset is ET40 for your bolt pattern of 5x112, which would mean the inner and outer clearance would change by;
Inner clearance; 2mm less
Outer clearance; the outer face of the wheel would stand out 24mm more than your current wheels, so almost an inch closer to the wheel arch edge. Bear in mind that you'd need wider tyres on an 8.5" wide wheel, which would likely add a few extra mm's to the 24mm additional 'poke', so you may have rubbing issues with the tyres fouling the bodywork (if you're lowered). Would an extra 24mm-plus additional tyre width extend the tyres beyond the bodywork? If so, I think that might be an MOT fail. Link to wheel offset calculator below so you can see the impact that different offsets will have on wheel clearance;http://www.1010tires.com/Tools/Wheel-Offset-Calculator
If your current wheels are unmarked, I think I'd stick with them and save yourself the cost of powder coating or buying wider wheels/tyres that might give you clearance issues.