Better than Galxy Ace but not more than 150 euro. Possible?

Both the G300 or the Xperia J are single core 1Ghz cpus. The Ace is a 800mhz so theres very little difference between them and the ace. Slightly bigger screen and a new version of Android though. I'd suggest if you want something faster than the ace you need to get something with a Dual Core processor. I would say to get a dual core under 200 you have to go 2nd hand.

Galaxy Ace 2 (3.8" screen and still on 2.3.6 but 4.1 expected) You get these around 130~150
Xperia P short battery life and no MicroSD slot, but on 4.0 around 160 ish.
Galaxy SII around 200~250.

You could consider a windows phone, as the windows phone OS is a lot nippier than android. But you either like that or not.