Which Marantz SACD player sounds better?

Anyone has compared SA14 v2, SA12, SA15 and SA11? Is the new one better than the old one? I am thinking about getting the SA15. I want to use it as a transport.

If playing SACD, is SA15 better than SA14V2 and SA12?
I have the SA8260. It doesn't sound very good on SACD.

If used as transport, are the 4 models mentioned above will outperform SA8260?

None of the aboove. Find a Marantz SA-1 reference player and end your search. There is a reason why the Marantz SA-1 cost over $7500.
Rather than dismiss your question by recommending a $7500+ player that you didn't ask about, I can endorse the SA15 relative to the 8260. I own both and can unquestionably state that the SA-15 sounds better than the 8260 (significantly better IMO). That fact alone justified the upgrade for me. Now, with respect to your question about how the SA15 might stack up against the SA11,12, or 14 I can't say. I've never done this comparision. I do not doubt that the $7500 SA-1 sounds better than the SA-15; for the difference in cost it certainly should.
Edmund, of the four models you mention, I would say the SA-11 sounds the best overall. There is definitely a law of diminishing returns though. The SA-15 is very good, and comes close to the SA-11 for almost half the price.

As for buying a Marantz to be used as a transport, this would confuse me, as I think the strengths of these players are their DAC's, not their transport section. You could save money by buying another, less expensive unit if you were simply planning to use it as a transport. A Sony or Teac possibly.

That's just my $0.02.