Mike,
When MB put the V8's in the W124 they sourced allot of parts from the SL's. 500E brakes may not fit inside the stock 15" wheels. Looking at the 500E I don't think there is an extra inch of clearance under its 16" wheels. I have not measured or anything, just a visual "guesstimation". A brand new setup with the updated parts should give you more than enough stopping power for a stock setup. Don't expect a race ready 911, but it will be more brakes than the 195/65/15 tires can handle for certain. Make sure the brake lines, calipers, fluid, and whatnot are all up to spec as well. Brakes are one of those "weakest link" things.

Lee

Lee