I had 6 weeks of annual leave saved up. Im changing to a job that pays significantly more than my current salary. When my boss asked me what it would take to stay, I asked for a salary increase of 35% which he begrudingly gave me. Then I quit. This equated to an entitlement payout of about $10,700 instead of $8000 on my previous rate, an extra $2700. And the new job still pays more than the increased rate I asked for.
This is pretty much what I did, although it was coincidental. Felt bad for my boss because he fought pretty hard to get a meaty pay rise for me, and then a month later I quit.
Dont feel bad for them. The company is doing more money, and if they ultimately give you a rise, that means you were working while you could have made more money.