Might not be a bad idea to purchase an un-moded UA-5 for Oade first... so if you want to get the W-Mod at some point later in time, you can... From what I have read, Oade won't mod one that wasn't originally purchased from them...
I have also read that stock, the UA-5 preamps don't sound that good, but I can't testify myself... only what I read. What I can tell you is that the warm mod UA-5 rox.
Peace-
pfife