Tim,
Small price penalty? Are you sure of what you're talking about? There are four possible engines on the DA42's - They originally came out with the Thielert 1.7's, and just before Thielert went belly-up they switched to the Thielert 2.0's. Now Thielert is back and you can get Thielert 2.0's again but Diamond got the shaft from Thielert so they quickly put together a Lycoming IO-360 conversion and at the same time developed the Austro diesel used in the DA42NG.
I think you can upgrade the Thielert 1.7's to Thielert 2.0's for "a small price penalty" but I think that upgrading from any Thielert-equipped DA42 to the Austro engines is quite costly. Engines, mounts, nacelles, parts of the fuel system, computers, yadda yadda - All has to be replaced, and I believe it's quite costly.
Yup -
According to Diamond, the upgrade is 99,000 Euros, which is currently about $140,000. Not a "small price penalty" in my book!