[Q] Moving from HTC Desire to S5 Mini, how to keep app data? topic

Hello,

I'm the new owner of a S5 Mini (G800F) with the latest OTA update and moving from an HTC Desire under rooted 2.3.3 is quite impressive.
But now, I'd like to move my data from the old phone to the new one. I have read around to find out how to do this and came up with two solutions:

1. Root the S5 Mini and use Titanium Backup to selectively restore what I need
2. Use Helium Backup to get data from the Desire and then selectively restore what I need on the S5 Mini

My problem is that rooting the S5 Mini will trigger the Knox counter and thus void its warranty. I'd like to avoid that at least for a while and so it seems that option 1 is not possible for me.
I went looking for another solution and saw that Helium backup was highly recommended. Unfortunately, the Android App is not available for the Desire under 2.3.3 and so this seems like a dead end as well.
Now, would it be possible to get Helium to use data created by Titanium backup? Or would it be possible to extract the data from the Desire in a way that Helium would be able to use?

Any help would be much welcome.

Regards.