Where can I find a good, challenging IT job?
Finding a job is one thing. Finding a job that pays well enough to make relocating a realistic option is another.
Your best bet is to get employed by a foreign company at foreign pay rates. This usually isn't a viable option unless you are able to work at least as a project manager, research director, regional sales/marketing manager or very high-level specialist/consultant. Otherwise, you'd be paid the going Polish wage, which is not at all that attractive, especially if you have a family to support. You might be able to leverage your knowledge of languages into a pay increase, but that depends on the particular employer and job in question.
Contact international companies like HP, Nokia and IBM and see if they have any high-paying job opportunities that fit your qualifications and experience in Poland. It's best to land a job
BEFORE you come. Competition is tight, especially for well-paying jobs, and you will be at a disadvantage not knowing the local language and having only a bachelors degree, though your experience could count for something.