To get the same fuel economy with a six cylinder W202 as your E320 you need a '98-99-00 with the M112 V-6 and 5-speed transmission.

I have a 1995 C280 with the M104 and a 2000 C280 with the M112. The '00 gets 2-3 mpg better economy.

But finding a really nice one at $5K will be work. There are a lot of W202's at low prices, but they are pretty used up.