I have a YAK 54 140 size. What engine should I get? I have all os engines now 4- .46.s, 1-.61 I

1) I want to put an OS 160($299) in it, but I like the
2) SAITO 125 (More expensive). I've never had a gas engine but I was thinking about getting a
3) Fuji Imvac. What do you guys think?