if the 528 is a sport package i would go for it. the 5 is a smooth driving well handeling car. as for if you want to mod it swap the head lights and tail lights out for newer style ones. if your wanting more power ess or vf can put you over 300 to the wheels (not a ton but its enough to be fun) and the m52 is happy with spray.

then again i'd rather have a nice 4 door over a coupe.