Personally I'd say don't lower it. I think R8s look just fine at their normal height. I like the standard SEi alloys too, but some of the later MG ones really suit the shape well.
I vote lower it slightly (properly, not just springs or a rubbish Gmax kit), fit later ZR or 25 GTI wheels, and then GIVE ME THE WHEELS YOU HAVE NOW pretty please.
Most people rate the Gmax kit as pretty good. If you lower as much as in the pic above you'll find that the front is too low and will hit ever speed bump out there! The blue car I posted up is about as low as is practical and I actually raised the suspension from what it was previously to get it to that height!
G max kits work fine with the gas shocks, 40 mil is just about right ride hieght and comfort isnt compromised to much. I did change my tyres from 40s to 45s though on my 17s and fitted a strut brace to tighten up the front end. I live in south wales and have to put up with the worst roads you can imagine, lots of huge pot holes, ruts and of course speed bumps. your alloys look mint, mine were the same. I got £120 for mine with nuts and lockers. Paid for the lowering
this is what a 40 mil drop with 17s looks like on my 214sei