An upgrade to the CR18's in the 650A would offer the greatest benefits as it would lighten the bike and greatly improve the wet weather performance although the braking really improves when you upgrade the brake pads to Kool Stops.

Using other wheel sizes requires a lot more changes to the fenders and brakes and will alter the performance of the bike.

Swapping the crank is a more involved process but will drop as much as a pound off the bike... I am partial to the Raleigh Heron cranks and the generic cranks Raleigh used on their sub brands tend to be of much poorer quality.

Drop bars and flipped North Roads can change the bike a great deal and this works for lots of people... this Raleigh Sports came into our shop as a drop bar model and is a very nice riding bike on those 650A's.