When I was a retailer, I sold several ARE Wilwood kits and feedback from those I spoke to again was positive. Tom Quad on here uses them and likes them.

The limit you have with 15" wheels is the impediment with rotor size and ultimately leverage. The biggest you can go with 15" rims is a 12.19 kit, and that is iffy. The 11.75 is a pretty reliable fit.

But using just the Wilwood calipers do gain you a couple of things. First is reduction in weight of 6# per wheel, but most importatnly, you gain a large selection of pad compounds to match the drving you are doing for improved fade resistance.