I've been doing a bit of info finding on this as well.
People seem to recommend FK spacers. Below 10mm (each side) you won't be able to get Hubcentric, just flat ones, as the existing lip on the hub doesn't extrude enough.
With 10mm (5mm each side that is) ones you should be okay with standard bolts and non hubcentric (System A), anything more and your looking at extended bolts and hubcentric spacers (System A centric). The (B centric ones) are the ones that bolt on to the hub individually, then your existing bolts hold the wheel on the hubcentric spacer.
I was recommended this site, and it explains everything quite well.
Remember though the size is altogether, so for 5mm each side you'd be looking at 10mm ones, and 25mm each side 50mm ones, and so on.
These also don't come with the extended bolts, so you'd need to get them seperate (apart from B centric!)
but its all explained if you read anyway:
http://www.venommotorsport.com/product_details.php?id=2794&manufacturer=FK&category=Wheel