The first CD (it's actually from 1992) on Warner Bros has the best sound, in the sense that it's un-futzed-with. There's not a HUGE difference in the later CDs but the '92 release sounds closest to the original LP, to my ears anyway. Same goes for the Warner
Field Day CD.
The Warner version of Downtown also happens to be the cheapest CD version available

, out of print but easily had from Amazon's third party dealers:
http://www.amazon.com/dp/B000002L85/?tag=imwan-20