Zen50 is great value and a superb flying machine. I have one with a YS63. Also a Zen 90 with a YS120.
If you want to go more exotic at a lower cost, try kits from the link shown below or go for the ZEN140 with a YS140 (thats next for me)

http://home.att.net/~rc-enterprises/...rprises001.htm