Hello Oz!
Well, you are in the middle of a dilemma... all these eyepieces are nice, but it's hard to get a final word on them, since most likely we've had one, or the other, but doubt there's a comparison made by the same person...
I personally had the UO 32mm KonigII, and loved it! quality is great, views are very nice... but ended up selling it because I wanted a lower mag wider field eyepiece, so ended up buying a UO 40mm MK-70... (a little more expensive than the ones you mentioned, but it is an awesome eyepiece!)
The Proxima might give you a wider FOV, but I have not had any experience with it to tell you if it is a better eyepiece overall... the UO 32mm was indeed a very nice one though...
As far as Siebert eyepieces goes, I've heard good and bad... but have not had a chance to test them personally.
Clear skies my friend, and good luck on your decision! (no matter what you decide, they all seem to be nice eyepieces!)
Ivan

P.S.
Also, check this review on some of them at CloudyNights...
http://www.cloudynights.com/eyepieces/Six%20Low%20Cost%202.html