Easiest (and maybe the cheapest too) down-converter for 455 kHz IF is the design by young Bill, KE1GF.
Steve,
I think it would be a pretty close tie...
Unless you already have the parts on hand, and want to
"dead-bug" the circuit... which would certainly work.
The NE602 is usually about $3 or $4 bucks, plus shipping ( and whatever misc parts you need)
The oscillator is about $5.
For convenience of having a pc board ready-made, and all the circuit-board parts for $12 (including shipping) is hard to beat.
In this thread....
http://amfone.net/Amforum/index.php?topic=6744.0Stu AB2EZ made a post, with a link to Bill's converter.