Not realy, completely different cars, completely different markets. The Caddy seems like more of a bruiser. Its not hard to make a saloon that will out perfom the M5 on the road. It's the other stuff that it does tot he driver that makes the sticker price of the M5 palletable. The Caddy may rip the asphalt from the ground, butI bet it still has a hollow plastic interior, i.e. it'll be fast, it'll be expensive, but it will still feel cheap.
And, it also looks goofy. Fender flares? It's too tall, something about it just doesn't look right. More wheel, less ground clearence, please.